FILE PHOTO: Iran's national flags are seen on a square in Tehran February 10, 2012, a day before the anniversary of the Islamic Revolution. REUTERS/Morteza Nikoubazl/File Photo

DUBAI (Reuters) - Iran is determined to reject demands by U.S. President Donald Trump for changes to its nuclear accord, which amount to bullying, a senior Iranian security official said on Saturday.

Trump has said that unless European allies rectify “flaws” in Tehran’s 2015 nuclear agreement with world powers by May 12 he will refuse to extend U.S. sanctions relief for Iran.

“This is an international agreement ... and we certainly have the capacity to defeat your bullying,” Ali Shamkhani, secretary of Iran’s Supreme National Security Council, said in remarks broadcast on state television.

“You are saying that you do not accept something that was set up under the last president and it should be changed,” Shamkhani said, addressing Trump.

“Who, then, guarantees that if something is done with you, the next president won’t come and refuse to accept it?”