President Trump speaks while meeting with Harley Davidson executives and union representatives at the White House. At the end of the event, Trump said that “nothing is off the table” in relation to current disagreements between the United States and Iran. (Win Mcnamee/Getty Images)

The United States and Iran traded threats Thursday as both nations sought new footing in a power struggle that could jeopardize the landmark international nuclear accord that President Trump has called “the worst deal ever negotiated.”

The Trump administration was preparing additional economic penalties on Iran related to the country’s recent ballistic missile test, with an announcement expected as soon as Friday, according to a U.S. official.

When asked whether his administration’s tough new posture could mean a military strike, Trump answered, “Nothing’s off the table.”

That followed the White House broadside Wednesday in which national security adviser Michael Flynn warned that Iran is “on notice” over the test launch. He also cited Iran’s support of rebels seeking to overthrow a U.S.-backed government in Yemen.

“This is not the first time that an inexperienced person has threatened Iran,” Ali Akbar Velayati, a senior adviser to Iran’s supreme leader, was quoted by Reuters as saying Thursday. “Iran does not need permission from any country to defend itself.”

(Reuters)

Speaking to reporters, Velayati brushed off what he called Trump’s “baseless ranting” and pledged that missile tests would continue as Iran sees fit.

The exchange surrounding the missile test is the most substantive between the two countries since Trump took office two weeks ago and suggests that each nation is willing to escalate tension at the outset.

The posturing on the U.S. side appears to be mostly an attempt to seize the upper hand in what Trump officials have said will be a far tougher, less forgiving relationship with Tehran. Flynn directly blamed Barack Obama’s administration for emboldening Iranian aggression and regional ambitions, and Trump has ridiculed his predecessor for seeking more cordial, if wary, relations.

Trump is under political pressure to make good on campaign pledges to get tough on Iran, while Iran has a history of testing the resolve of new U.S. leaders. The Iranian leadership also faces domestic political pressures with a presidential election due this spring.

“It will take him a long time and will cost the United States a lot, until he learns what is happening in the world,” Iranian President Hassan Rouhani said in a televised address Wednesday, in which he also accused Trump of discrimination and recklessness.

Rouhani, considered a cautious political reformer, presided over the partial warming of the three-decade freeze in U.S.-Iranian relations under Obama.

Rouhani said that Trump, in temporarily halting travel to the United States from Iran and six other Muslim-majority nations, is “trampling on all international principles and commitments.”

Iran had earlier vowed “reciprocal measures” for the ban, and the missile launch Sunday was widely seen as a test of the new U.S. administration.

It is not clear whether the launch violates a U.N. Security Council edict, but the Trump administration maintains that it does. The United States called an emergency Security Council review of what it called a “provocative” breach.

“Clearly, we wanted to make sure that Iran understood that they are on notice this is not going unresponded to,” White House press secretary Sean Spicer said.

White House officials have refused to clarify the “on notice” statement either on record or anonymously, but it could indicate additional economic sanctions, military repositioning or the first moves to undermine the nuclear accord that the Obama administration counted as a signature foreign policy accomplishment.

Iran experts in the United States have said the most likely initial sanctions would probably mirror those Obama applied last year to Iranian companies and individuals that Washington accused of involvement in the country’s ballistic missile program.

Most Republican senators assumed that sanctions are what Flynn had in mind from his comments Wednesday.

“We should stop the crap. I think I know what he means. . . . More sanctions,” said Sen. Lindsey O. Graham (R-S.C.).

The new sanctions were first reported by Reuters.

House Speaker Paul D. Ryan (R-Wis.) said Thursday that he is in favor of new sanctions on Iran. Legislation is already in the works, but Republicans would need some Democratic support to reimpose penalties.

“I would be in favor of additional sanctions on Iran,” Ryan told reporters. “I’d like to put as much toothpaste back in the tube as possible. I think the last administration appeased Iran far too much.”

Karim Sadjadpour, an Iran analyst at the Carnegie Endowment for International Peace, said the new administration’s view of Iran is informed by much more than deep skepticism about the nuclear deal and fear over Iran’s potential threat to Israel.

“For Trump’s senior national security brain trust, including Flynn, [Defense Secretary Jim] Mattis and key NSC staff, the enmity toward Iran is very personal,” Sadjadpour said. “They hold Tehran directly responsible for hundreds of U.S. military deaths in Iraq.”

As a Marine general, Mattis was a commander in Iraq and later head of the military region responsible for both the wars in Iraq and Afghanistan.

Trump reiterated on Twitter on Thursday that Iran is “formally PUT ON NOTICE for firing a ballistic missile. Should have been thankful for the terrible deal the U.S. made with them!”

Perhaps for emphasis, Trump followed that with a tweet specifically about the nuclear deal.

“Iran was on its last legs and ready to collapse until the U.S. came along and gave it a life-line in the form of the Iran Deal: $150 billion,” he wrote.

Most experts place the amount Iran recouped in frozen assets closer to $100 billion.

There is little chance that Trump will immediately rip up the 2015 deal designed to prevent Iran from developing a nuclear weapon. Trump has not set out any plan in detail, but he has spoken of strengthening enforcement of the deal and improving on it. The United States would need the agreement of the other signers, including Russia and China, to renegotiate it.

Secretary of State Rex Tillerson was critical of the deal during his confirmation hearing last month but said it could be improved.

A U.S. official who briefed reporters after Flynn’s announcement Wednesday said the new administration is keeping potential retaliatory actions strictly separate from the nuclear deal, although U.S. officials acknowledge that anything that affects the U.S.-Iran relationship has implications for the future of the pact.

Few congressional Republicans are demanding an outright rejection of the nuclear accord, either, and say they are working with the new administration to tighten enforcement and raise the stakes for Iran for any violations. U.S. allies including Saudi Arabia and Israel, which worked to thwart the deal, now have an interest in keeping it in place for fear of the instability that could result from abandoning it.

The 2015 deal lifted international trade and other restrictions on Iran related to its nuclear program in exchange for a halt in the most troublesome aspects of Iranian nuclear development. Iran claims it is not seeking a nuclear weapon.

The deal left in place separate U.S. sanctions that could now be expanded or tightened.

The risk analysis and policy organization Eurasia Group assesses a 60 percent probability that the deal survives but said in a memo Thursday that “there is now initial downward pressure on that number.”

“Trump is unlikely to tear up the deal and shoulder the full wrath of the international community,” the memo said. “Trump will walk a fine line, and probably try to keep the deal intact.”

Erin Cunningham in Istanbul and Karoun Demirjian in Washington contributed to this report.