TEHRAN — Iran’s supreme leader on Wednesday hinted at stepping up his country’s nuclear program, signaling a possible escalation in an already volatile relationship with Washington after President Trump announced he was pulling the United States out of the 2015 nuclear deal.
Mr. Trump said on Tuesday that the United States would leave the agreement, under which Iran agreed to strict limits for 15 years on its development of nuclear fuel, to prevent it from developing nuclear weapons, in return for an easing of economic sanctions. In withdrawing from the deal, Washington would reimpose sanctions.
Iran has always insisted that its uranium enrichment was intended only to operate nuclear power plants and conduct research, but it also put Iran closer to producing fuel that could be used in atomic bombs.
“Last night, you heard the president of America making petty and mindless statements,” Ayatollah Ali Khamenei, Iran’s supreme leader, told a group of teachers in his Tehran office, according to the semiofficial news agency Fars. “There were perhaps more than 10 lies in his statements.”
“He threatened both the system and the nation that ‘I will do this and that,’ ” the ayatollah added. “I say on behalf of the nation of Iran: ‘Mr. Trump, you won’t do a damn thing!’ ”
The other parties to the deal — Britain, China, France, Germany, Russia, and the European Union — continue to support it. Western intelligence agencies say that Tehran has long had an eye toward — and at times has actively pursued — nuclear weapons.
Yukiya Amano, the head of the International Atomic Energy Agency, said in a statement on Wednesday that Iran was “subject to the world’s most robust nuclear verification regime” and that his nuclear watchdog agency “can confirm that the nuclear-related commitments are being implemented by Iran.”
It was Ayatollah Khamenei who ultimately approved the compromises made in the nuclear agreement in 2015, though he also warned at the time against trusting the Americans.
President Hassan Rouhani of Iran said on Tuesday that his country would continue to abide by the agreement, but Ayatollah Khamenei, the spiritual leader for the past 29 years, wields the ultimate power in the nation. On Wednesday, the ayatollah seemed to suggest that Iran, too, could abandon the deal.
“When the nuclear issue started, some of the elders of the country said, ‘Why the insistence on keeping the nuclear power, let it go,’ ” the ayatollah said. “Of course, this was a wrong thing to say. The country needs nuclear power and according to experts, the country will need 20,000 megawatts of nuclear electricity.”
Israel, Saudi Arabia and the United States say they want to halt Iran’s development of missiles, but if Tehran were to agree to those demands, “they will bring up other things,” the ayatollah said.
Reacting to reports that Mr. Trump wants to force “regime change” in Iran, the ayatollah said, “wait for the day when Trump is dead, his corpse is fed on by snakes and insects, but the system of the Islamic Republic will still be standing.”
Iranian officials involved in nuclear negotiations say the focus will now be on how European parties to the deal react to Mr. Trump’s announcement. The sanctions that the American president promised to revive actively discourage and punish European companies and Asian buyers of oil that do business with Iran.
European officials — still committed to the Iran deal but eager to avoid American penalties — appeared to be unsure of how to respond. “It falls to the U.S. administration to spell out their view of the way ahead,” Boris Johnson, the British foreign secretary, said.
Ali Khorram, a former Iranian ambassador to China and adviser to the country’s nuclear negotiating team, said that Mr. Trump had “violated all international norms that come with such an agreement.”
“If European companies are banned by America to do business with Iran, it is up to Europe to negotiate a solution with the U.S.,” he added.
Iranian military commanders welcomed Mr. Trump’s decision, the semiofficial news agency ISNA reported. “Iranian people never favored the nuclear deal,” the chief of staff of the Iranian Armed Forces, Maj. Gen. Mohammad Bagheri, was quoted as saying.
Iran already faces a severe economic crisis, with high unemployment, drought, and a weakening currency.
But Iranian hard-liners expressed joy at Mr. Trump’s decision. “Now all Iranians blame the United States for their troubles,” said Hamidreza Taraghi, a hard-line political analyst.
On social media, many Iranian users shared a hashtag, #untr_US_table, to signal their anger at the United States.
Oil markets were jittery on Wednesday, with Brent crude up nearly 3 percent at nearly $77 a barrel, the highest level since late 2014. Traders expressed fear that American sanctions would cut Iranian oil exports, shrinking supplies in an already tight market.
On Wednesday, Saudi Arabia, the world’s largest oil exporter and an adversary of Iran’s, tried to calm the markets. The Energy Ministry released a statement saying that the kingdom “would work with major producers within and outside OPEC as well as major consumers to mitigate the impact of any potential shortages.”
The actions of Saudi Arabia, which applauded President Trump’s decision, will be closely watched as the Iran confrontation plays out. Saudi Arabia is the only oil producer that can quickly add large volumes to its output.