US President Donald Trump said that “nothing is off the table,” when it came to a response to Iran’s controversial test this week of a ballistic missile capable of carrying a nuclear warhead.

Speaking to reporters Thursday, Trump was responding to a question about whether a military response to Iran was under consideration.

“Nothing is off the table,” he replied, borrowing a phrase Prime Minister Benjamin Netanyahu has used for years vis-à-vis Tehran’s nuclear program.

Trump’s comment followed a string of remarks by Republican senators, including the House Speaker, backing additional sanctions on Iran in the wake of the missile test, which prompted an emergency UN Security Council session and a call by Netanyahu to reimpose punitive measures.

“I would be in favor of additional sanctions on Iran,” House Speaker Paul Ryan said at a weekly press conference on Thursday. “We need to have a tough-on-Iran policy… We should stop appeasing Iran.”

“I think the last administration appeased Iran far too much. I think they went too far with Iran and I think as a result Iran is far more activist than it otherwise would be,” he said.

In this Sept. 21, 2016 file photo, House Speaker Paul Ryan of Wisconsin speaks during a news conference on Capitol Hill in Washington. (AP Photo/Manuel Balce Ceneta, File)

“Iran, don’t forget … is the biggest state sponsor of terrorism in the world. Iran writes on their missiles in Farsi, Hebrew and English ‘Death to America’, ‘Death to Israel’ and then tests them. So this is not a friendly country that has global peace or national security interests in their minds,” Ryan added.

Trump had earlier on Thursday tweeted that “Iran has been formally PUT ON NOTICE for firing a ballistic missile. Should have been thankful for the terrible deal the US made with them!” echoing remarks made Wednesday by his national security adviser, Michael Flynn.

Iran has been formally PUT ON NOTICE for firing a ballistic missile.Should have been thankful for the terrible deal the U.S. made with them!

— Donald J. Trump (@realDonaldTrump) February 2, 2017

Also Thursday, Senator Bob Corker, the chairman of the Senate Foreign Relations Committee, told Reuters, “I think there’s a lot that we can do, now, that we were unable to do before to push back against Iran,” adding that the committee was “in the early stages” of working on legislation related to the nuclear deal.

“The administration, thankfully, is going to follow through on appropriately holding Iran accountable for the violations that are taking place,” he said.

Senator Lindsey Graham joined the chorus Thursday, telling CNN that “the world should not only condemn Iran but we should have multi-national sanctions against the regime for their continued violation of the UN Security Council resolutions regarding their missile program.”

On January 29, Iran is said to have tested a 4,000-kilometer (2,500-mile) ballistic missile capable of carrying a nuclear warhead. On Thursday, the German newspaper Die Welt reported that Iran also tested a home-made cruise missile with the same capabilities: The Soumar, with a range of up to 3,000 kilometers (1,864 miles), flew 600 kilometers (373 miles) on its maiden voyage, according to the German report.

It is reportedly a re-engineered Russian KH-55 cruise missile, which is capable of reaching Israel from Iran, and has the advantage that it can be launched from ships, aircraft and submarines.

The Soumar cruise missile at its unveiling in March 2015. (YouTube screenshot)

The missiles are not covered by UN Resolution 2231, which was passed shortly after the nuclear deal with Iran was signed in July 2015 and calls on Tehran “not to undertake any activity related to ballistic missiles designed to be capable of delivering nuclear weapons, including launches using such ballistic missile technology.” Iran argues that its ballistic missile program is also not covered by the resolution because it does not have a nuclear weapons program.

During his campaign, Trump promised both to “dismantle the disastrous deal” and to “force the Iranians back to the bargaining table to make a much better deal, but in a call to the Saudi king on Sunday promised to “vigorously enforce” the controversial agreement.

Netanyahu on Thursday demanded the reimposition of sanctions against Iran, terming the test a “flagrant breach” of UN Security Council resolutions, and said he would discuss with Trump a reevaluation of the “entire failed nuclear accord” during their February 15 meeting in Washington.

DUBAI, United Arab Emirates (AP) — By putting Iran “on notice,” the new US administration is laying the groundwork for a more confrontational approach toward the Islamic Republic.

What that means in practice is anyone’s guess, since the White House isn’t saying. That is in line with President Donald Trump’s desire to keep America’s adversaries guessing and boost US leverage.

The US has plenty in its toolbox should it choose to confront Iran more aggressively, from ratcheting up sanctions all the way to full-out war. Each carries real risks.

That’s because Iran, however unpopular in Washington, is not a failed-state pushover. It is sure to respond if it feels it is under threat.

Here are some of the main issues:

Why is Iran ‘on notice?’

In his surprise appearance in the White House briefing room, Trump’s national security adviser, Michael Flynn, blasted Iran for threatening American allies and “malign actions — including weapons transfers, support for terrorism, and other violations of international norms.”

He also linked Iran directly to missile attacks by Yemeni Shiite rebels known as Houthis on Saudi and Emirati ships. Saudi Arabia and the United Arab Emirates are leading a coalition supporting Yemen’s internationally recognized government against the Iranian-backed rebels. Iran denies arming the rebels.

US National Security Adviser Michael Flynn speaks during the daily news briefing at the White House, in Washington, Wednesday, Feb. 1, 2017. (AP Photo/Carolyn Kaster)

What appeared to trigger the notice being served, however, was Iran’s Sunday launch of a medium-range ballistic missile. A UN Security Council resolution prohibits Iran from testing ballistic missiles specifically designed to carry a nuclear warhead.

The US and Iran disagree on whether this and previous launches — including one in March 2016 involving a missile emblazoned with the phrase “Israel must be wiped out” in Hebrew — violate the ban.

What happens next?

Senior Trump administration officials have said they are considering options including economic measures and more support for Iran’s regional rivals.

Among the biggest of those adversaries are Saudi Arabia, Israel and the UAE, whose foreign minister has voiced support for Trump’s decision to temporarily block entry to citizens of Iran and six other Muslim-majority countries.

The Saudis and Emiratis would welcome deeper American involvement for the war in Yemen, which they view in large part as a proxy fight against Iran. The US has provided logistical support to the Saudi-led coalition since it intervened in March 2015, but in December the Obama administration halted some arms sales to the Saudis over concerns about civilian deaths.

Washington could implement further unilateral sanctions against Iran. Nuclear-related sanctions were removed last year after Iran agreed to a deal with world powers limiting its nuclear activities, but Washington has maintained other sanctions related to support for terrorism and other actions as far back as the 1979 Islamic Revolution.

Torbjorn Soltvedt, a Middle East analyst at risk consulting firm Verisk Maplecroft, predicted that any new sanctions related to ballistic missile tests would target Iran’s engineering industry.

“There is no doubt now that further flare-ups could translate into additional sanctions,” he wrote.

The view from Iran

Iran is as distrustful of the United States as Washington is of Tehran, and the countries’ views of one another often seem like distorted mirror images.

From Iran’s perspective, the US is a meddlesome outside power that has kept it surrounded for years with warships and troops in neighboring Afghanistan and Iraq.

File: The USS Stennis on its way to the Persian Gulf in 2012. (Department of Defense/Randi R. Brown, US Navy)

Iran has not responded directly to Flynn’s comments, although the Revolutionary Guard’s acting commander was defiant that it would continue its missile development program.

“Iran’s great missile power is one of the world’s unmatched deterrent powers today,” Gen. Hossein Salami was quoted as saying by the semi-official Tasnim news agency Thursday.

Iran’s leaders are likely to see any new US measures as a provocation in the wake of the nuclear deal.

The agreement was cheered by many in Iran because it lifted crippling economic sanctions and is opening up new business opportunities with the West, including a historic, $16.6 billion deal with Boeing to buy 80 US-made jetliners.

Is a military clash possible?

US officials have not confirmed whether military action is on the table. It’s unlikely to be the first step.

Maha Yahya, director of the Carnegie Middle East Center in Beirut, said a push for tougher sanctions or some form of diplomatic censure is more likely for now.

“It’s far too early in the game for us to see any kind of military moves,” she said.

US President Donald Trump in the White House February 2, 2017 in Washington, DC. (AFP/ Brendan Smialowski)

Still, US forces are already in place should Trump decide to launch at least a limited strike.

Guided-missile destroyers and other US warships attached to the Navy’s 5th Fleet routinely patrol the Persian Gulf and occasionally have unnervingly close encounters with Iranian Revolutionary Guard vessels. Just this week, 17 ships from the US, Australia, Britain and France took part in joint naval exercises in the Gulf.

At least one US aircraft carrier is usually in the region, although not right now. The nearest one was last reported to be in the Western Pacific.

The US does have warplanes capable of carrying out airstrikes stationed elsewhere in the region, including Qatar and the UAE. They have been actively targeting positions of the Islamic State group in Iraq and Syria.

How could Iran respond?

Iran is likely to calibrate its responses based on how the US acts.

Tougher US sanctions could convince Tehran to start reinterpreting the terms of the nuclear deal, said Mohammad Marandi, a political analyst in Tehran.

“The Iranians will reciprocate,” he said. “The more the Americans disregard the agreement … the more the Iranians will find new ways of interpreting the text that do not work to the benefit of the United States.”

Iranian President Hassan Rouhani gives a press conference in Tehran on Jaunary 17, 2017, to mark the first anniversary of the implementation of the nuclear deal. (AFP/Atta Kenare)

More direct action could include an uptick in harassment of US warships by Revolutionary Guard speedboats in the Gulf, or new cyberattacks like one that crippled the network of Saudi Arabia’s state oil company in 2012.

Iran also could boost support for regional allies such as Lebanon’s Hezbollah or the Houthis in Yemen.

A military strike could elicit a much more damaging response.

Iranian officials have repeatedly vowed to shut the Strait of Hormuz at the mouth of the Gulf if Iran comes under threat. Doing so would stop the flow of a nearly a third of all oil traded by sea and likely draw the US into a naval battle.

Iran could also target US military bases or allied countries in the region with existing missiles, which it says can travel up to 2,000 kilometers (1,200 miles). Much of the Middle East, including Israel, falls within that range.

Copyright 2017 The Associated Press.