DUBAI (Reuters) - Iran will not be bullied by the United States and will react strongly to any "wrong move" by Washington on Tehran's nuclear deal, Supreme Leader Ayatollah Ali Khamenei said on Sunday.

U.S. President Donald Trump said on Thursday that Iran was violating "the spirit" of the 2015 deal under which it got sanctions relief in return for curbing its nuclear program.

State television quoted Khamenei as saying Iran was standing firm "and any wrong move by the domineering regime regarding the (nuclear accord) will face the reaction of the Islamic Republic."

Washington extended some sanctions relief for Iran on Thursday under the nuclear deal with world powers, but said it had yet to decide whether to maintain the agreement.

Trump must make a decision by mid-October whether to certify that Iran is complying with the deal, known as the Joint Comprehensive Plan of Action (JCPOA). If he does not, Congress has 60 days to decide whether to reimpose sanctions.

"Today, despite all the commitments and discussions in the negotiations, America's attitude toward these negotiations and their outcome is completely unjust and amounts to bullying," Khamenei said in a speech to Iranian police academy graduates.

"The Americans should know ...there will be no retreat by the Islamic Republic."

The Foreign Ministry in Tehran condemned as "continued Iranophobia" Washington's move on Thursday to impose sanctions on 11 individuals and firms, including two based in Ukraine, state news agency IRNA reported.

The U.S. Treasury accused the 11 of supporting Iran's ballistic missile program or its Revolutionary Guards, or engaging in cyber attacks against the U.S. financial system.

U.S. Secretary of State Rex Tillerson said on Sunday he believed Iran was in technical compliance with the nuclear deal but had stepped up destabilizing activities in Yemen and Syria and continued to have an active ballistic missile program.

"None of that, I believe, is consistent with that preamble commitment that was made by everyone" in the nuclear deal, he told CBS' "Face the Nation."

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ROUHANI INVITATION

Iran said last month it could abandon the nuclear agreement "within hours" if the United States imposed any new penalties, after Washington ordered unilateral sanctions over Tehran's ballistic missile tests.

Iranian President Hassan Rouhani, speaking on Sunday before leaving to attend a U.N General Assembly meeting in New York, said Washington should join the countries that continued to support the nuclear deal, which he compared to a dinner party.

"They can choose the right path and also enter the room where the food is served. We would not have a problem with that," IRNA quoted Rouhani as saying.

The United States imposed unilateral sanctions, saying Tehran's ballistic missile tests violated a U.N. resolution that endorsed the nuclear deal and called on Tehran not to undertake activities related to ballistic missiles capable of delivering nuclear weapons.

Iran denies its missile development breaches the resolution, saying the missiles are not designed to carry nuclear weapons.

(Reporting By Dubai newsroom; Additional reporting by Doina Chiacu in Washington; Editing by Susan Fenton and Peter Cooney)