Iran sent mixed signals Thursday as tensions with the U.S. appeared to ease, with President Hassan Rouhani warning of a “very dangerous response” if the U.S. makes “another mistake” and a senior commander vowing “harsher revenge” for the killing of a top Iranian general.

Both sides appeared to step back on Wednesday after Iran launched a series of ballistic missiles at two military bases housing American troops in Iraq without causing any casualties. Iran said the attack was retaliation for the U.S. strike that killed Gen. Qassem Soleimani, the architect of its regional security strategy, in Iraq earlier this week.

Rouhani said the strike on the bases was a legitimate act of self-defence under the U.N. Charter, but he warned that “if the U.S. makes another mistake, it will receive a very dangerous response.”

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In addition to launching the missile attack, Iran also abandoned its remaining commitments under the 2015 nuclear deal, which President Donald Trump had walked away from in May 2018. But Rouhani said Thursday that Iran would continue to co-operate with U.N. inspectors.

Senior Iranian military commanders struck a more defiant tone.

2:46 Trump won’t respond militarily to Iranian airstrikes, says Tehran “standing down” Trump won’t respond militarily to Iranian airstrikes, says Tehran “standing down”

Abdollah Araghi, a member of Iran’s joint chiefs of staff, said the country’s Revolutionary Guard “will impose a more severe revenge on the enemy in the near future,” according to the semi-official Tasnim news agency.

Tasnim also quoted Gen. Ali Fadavi, the acting commander of the Guard, as saying the missile attack was “just one of the manifestations of our abilities.”

“We sent dozens of missiles into the heart of the U.S. bases in Iraq and they couldn’t do a damned thing,” he was quoted as saying.

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On Wednesday, Trump signalled that he would not retaliate militarily for the strike on the bases. That raised hopes that the current standoff, which brought the two countries to the brink of an all-out war, may be winding down.

Rouhani spoke by phone Thursday with Prime Minister Boris Johnson, urging Britain to denounce the killing of Soleimani.

As head of Iran’s elite Quds Force, Soleimani had mobilized armed proxies across the region and was blamed for deadly attacks against Americans going back to the 2003 U.S.-led invasion of Iraq. In Iran, he is seen by many as a national hero who played a key role in defeating the Islamic State group and resisting Western hegemony.

2:49 Canadian Forces declared “safe” after Iran missile attack in Iraq Canadian Forces declared “safe” after Iran missile attack in Iraq

Without Soleimani’s efforts leading forces in Syria and Iraq against IS, “you would not have peace and security in London today,” Rouhani was quoted as saying by Vice-President Alireza Moezi, who tweeted about the call with Johnson.

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Downing Street confirmed the call, saying Johnson called for “an end to hostilities” in the Gulf. It said the U.K. stands by the nuclear deal and is urging Iran to return to full compliance.

Krauss reported from Dubai, United Arab Emirates. Associated Press writer Jill Lawless in London contributed.