Iran's president has issued another warning as meetings between President Donald Trump and France's Emmanuel Macron are underway in Washington.

Hassan Rouhani says the United States will face "grave" consequences if Washington decides to withdraw from the landmark 2015 nuclear deal between Tehran and world powers.

Rouhani spoke to a crowd of supporters in the city of Tabriz on Tuesday. State TV broadcast the speech.

He said the Iranian nation and government will "strongly resist" any plots by those who sit in the White House. He didn't elaborate except to say Tehran has abided by commitments.

Trump did not re-certify the deal in January but extended the main sanctions waivers and gave the Europeans until the next waiver deadline on May 12 to come up with fixes to the deal.