Iran's top diplomat accused U.S. President Donald Trump of "maliciously violating" Iran's 2015 nuclear deal after Trump threatened to pull out of the deal within months unless changes are made.

Trump's announcement is a "desperate attempt to undermine a solid multilateral agreement," Iranian Foreign Minister Mohammad Javad Zarif said on Twitter late on January 12, citing sections of the agreement that he said the United States is violating by demanding changes on matters already agreed to by Iran and the five other world powers that negotiated the deal.

The deal is "not renegotiable," Zarif said. "Rather than repeating tired rhetoric, the U.S. must bring itself into full compiance -- just like Iran," he said.

Trump earlier in the day said he once again would extend U.S. sanctions relief for Iran, as required under the deal in exchange for curbs on Iran's nuclear activities, but he intends to pull the United States out the agreement unless it is strengthened within months.

The president said in a statement on January 12 that he was granting a waiver on U.S. sanctions for another 120 days for the "last" time to provide time to negotiate changes with European powers to strengthen the accord, particularly by making permanent curbs on Iran's nuclear activities that currently are scheduled to expire within 10 years.

"Today, I am waiving the application of certain nuclear sanctions, but only in order to secure our European allies’ agreement to fix the terrible flaws of the Iran nuclear deal," he said in his statement.

"This is a last chance. In the absence of such an agreement, the United States will not again waive sanctions in order to stay in the Iran nuclear deal. And if at any time I judge that such an agreement is not within reach, I will withdraw from the deal immediately," he said.

"Either fix the deal’s disastrous flaws, or the United States will withdraw," he added.

The Trump administration on January 12 also announced new, targeted sanctions on 14 Iranian persons and organizations for "serious human rights abuses," censorship, and non-nuclear weapons issues, a Treasury Department spokesperson said.

The biggest name included in the new sanctions list was Sadeq Larijani, head of the Iranian judiciary and brother of Ali Larijani, who is speaker of the Iranian parliament.

The Treasury said Larijani was "responsible for ordering, controlling, or otherwise directing, the commission of serious human rights abuses against persons in Iran or Iranian citizens or residents."

Under the new sanctions, any assets that the people or entities have within U.S. jurisdiction will be frozen and Americans will be barred from doing business with them.

Iran vowed on January 13 to retaliate against the sanctions on Larjani.

"The Trump regime's hostile action...crossed all red lines of conduct in the international community and is a violation of international law and will surely be answered by a serious reaction of the Islamic Republic," Iran's Foreign Ministry said in a statement carried by state media.

By imposing a deadline in May for the U.S. Congress and European powers to strengthen the nuclear accord, Trump's declaration puts considerable pressure on Britain, France and Germany -- the European signatories to the nuclear pact with Iran.

Trump wants them to help the United States devise a new agreement designed to prevent Iran from escalating nuclear activity again next decade, as permitted under the 2015 arrangement reached by former President Barack Obama.

Since Iran has repeatedly spurned any effort to renegotiate the accord, one alternative suggested by Trump administration officials would be to reach agreement with the European allies to reimpose Western sanctions on Iran if it restarts efforts to develop nuclear weapons after curbs on its activities expire under the nuclear deal.

"I have been very clear about my opinion of that deal," Trump said in his January 12 statement. "It gave Iran far too much in exchange for far too little."

Iran has said its nuclear program is strictly for peaceful uses. It has said it will abide by the agreement as long as other signatories do, but warned that it would "shred" the deal should Washington pull out.

European Pressure

European signatories to the deal have pressured the United States to stick to the accord. They did not immediately react to Trump's demand on January 12 that they help come up with a stronger agreement.

The German Foreign Ministry said Berlin would consult with European partners on a common way forward after Trump’s declarations but that the country would "continue to campaign for the full implementation of the nuclear agreement."

Besides eliminating the so-called sunset clauses in the nuclear deal, Trump is also demanding that Iran allow more timely inspections of sites requested by the International Atomic Energy Agency.

In addition, he wants the deal to state that Iran's nuclear effort and its missile programs are inseparable. U.S. and other officials have complained that Iran's ballistic-missile program can easily be converted for nuclear use.

With reporting by RFE/RL's Mike Eckel, Mark Najarian, Reuters, and AP