* Supreme leader says Iran won't be bullied by United States
* President Trump had accused Iran of violating "spirit" of deal
* President Rouhani urges U.S. to abandon hostile policies (Adds Rouhani remarks, paragraphs 7-8)
DUBAI, Sept 17 (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.
His comments came after U.S. President Donald Trump said on Thursday that Iran was violating "the spirit" of the 2015 deal under which Tehran got sanctions relief in return for curbing its nuclear programme.
"The Iranian nation is standing firm and any wrong move by the domineering regime regarding the (nuclear accord) will face the reaction of the Islamic Republic," state television quoted Ayatollah Khamenei as saying.
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 waived under the deal.
"Today, despite all the commitments and discussions in the negotiations, America's attitude towards these negotiations and their outcome is completely unjust and amounts to bullying," Khamenei said in a speech to Iranian military academy graduates.
"The Americans should know that the Iranian people will stand firm on their honourable positions and on important issues related to national interests, there will be no retreat by the Islamic Republic," he said.
ROUHANI INVITES U.S. TO JOIN "DINNER"
Iran said last month it could abandon the nuclear agreement "within hours" if the United States imposes 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 the U.N General Assembly in New York, said the United States should join the countries that continue to support the nuclear deal, which he compared to a dinner party.
"They (United States) can choose the right path and also enter the room where the food is served. We would not have a problem with that," state news agency 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 upon Tehran not to undertake activities related to ballistic missiles capable of delivering nuclear weapons, including launches using such technology.
It stopped short of explicitly barring such activity.
Iran denies its missile development breaches the resolution, saying its missiles are not designed to carry nuclear weapons. (Reporting By Dubai newsroom; Editing by Susan Fenton)