Iran will not give in to US "bullying" as Washington attempts to undermine Tehran's nuclear deal with world powers, the Islamic republic's supreme leader Ayatollah Ali Khamenei said Sunday.

"Iran, which is a powerful nation, will not give in to pressure and will not bow," Khamenei said in an address to police officers in Tehran.

"The corrupt, lying, deceitful US officials insolently accuse the nation of Iran... of lying, whereas the nation of Iran has acted honestly and will continue on this path until the end in an honest manner," said Khamenei.

"The enemy should know that bullying may work in other parts of world, but it will not work in the Islamic republic."

President Hassan Rouhani left on Sunday for the UN General Assembly in New York, where he is set to hold crucial talks on the 2015 nuclear deal, which eased international sanctions in exchange for curbs to Iran's atomic programme.

US President Donald Trump has threatened to tear up the deal and his administration has been looking for grounds to declare Iran in non-compliance, despite repeated UN declarations that Tehran has stuck to its commitments.

"You are the liars. The nation of Iran is standing firm and any wrong move... will face a reaction by the Islamic republic," said Khamenei.