Hassan Rouhani spoke after French President Emmanuel Macron flew to Washington to try to persuade Trump not to scrap the 2015 agreement - under which Iran curbed its nuclear program in return for the lifting of sanctions.

"They say that with the certain leader of a European country we want to make a decision about a seven-sided agreement," Rouhani said in a speech broadcast live on state TV.

"For what? With what right?" he added.

He reserved particular scorn for the US president, who has called the agreement one of the worst deals ever negotiated and has threatened to restore US sanctions next month unless what he sees as severe flaws are fixed.

"You don't have any background in politics. You don't have any background in law. You don't have any background on international treaties," Rouhani said.

"How can a tradesman, a merchant, a building constructor, a tower constructor make judgments about international affairs," he added referring to Trump's career as a property developer.

The other powers that signed the agreement with Iran - Russia, China, Germany, Britain and France - have all said they want to preserve it. Many in the West see it as the best hope of preventing Iran from getting a nuclear bomb and heading off a nuclear arms race in the Middle East.

Earlier Trump warned after talks with Macron: "If (Iran) restart their nuclear program, they will have bigger problems than they have ever had before."

In a bid to salvage the deal while satisfying Trump's call for tougher action, Macron's has proposed that the United States and Europe block any Iranian nuclear activity until 2025 and beyond, address Iran's ballistic missile program and generate conditions for a political solution to contain Iran in Yemen, Syria, Iraq and Lebanon.

German Chancellor Angela Merkel will hold talks with Trump in Washington later in the week.

Australian Associated Press