Iran deal to dominate agenda as France's Macron visits US

French President Emmanuel Macron met his American counterpart Donald Trump on Monday as part of a state visit likely to be dominated by differences with Washington over trade and the nuclear accord with Iran.

As Macron headed to the United States, the Iranian government urged European leaders to convince Trump not to tear up the 2015 deal between Tehran and six world powers.

The French president said on Sunday there was no "Plan B" for keeping a lid on Tehran's nuclear ambitions.

He is on something of a rescue mission for what is formally known as the Joint Comprehensive Plan of Action (JCPOA), which Trump has said he will scrap unless European allies fix what he calls "terrible flaws" by mid-May.

"This visit is very important in our current context, with so many uncertainties, troubles and at times threats," Macron said as he arrived in Washington.

Iranian Foreign Minister Mohammad Javad Zarif called on European leaders to support the agreement.

"It is either all or nothing. European leaders should encourage Trump not just to stay in the nuclear deal, but more important to begin implementing his part of the bargain in good faith," Zarif wrote on Twitter.

The deal reached between six powers - all of whom but Germany are nuclear-armed - and Tehran put curbs on Iran's nuclear programme in exchange for sanctions relief.

Minutes after Macron touched down in the United States, the White House said it had no announcements on the Iran deal.

"The president has been extremely clear that he thinks it's a bad deal. That certainly has not changed," said White House spokeswoman Sarah Sanders.

Macron said on "Fox News Sunday" it would be better to protect the deal than to get rid of it.

"Is this agreement perfect and this JCPOA a perfect thing for our relationship with Iran? No. But for nuclear, what do you have as a better option? I don't see it," he said.

While the French leader has tried to develop a close relationship with Trump since he took office last May, he has so far seen few tangible results on issues from Iran to climate politics.

Macron brought with him an oak tree sapling for planting on the South Lawn of the White House. The tree came from the Belleau Woods, site of a World War One battle in 1918 where 9,000 Americans died. Trump and Macron shovelled dirt on the freshly planted tree as the cameras clicked. "France is a very special country," said Trump. "It's a great honour."

Working meetings will be held at the White House on Tuesday before Macron addresses Congress the following day, the anniversary of the day French General Charles de Gaulle addressed a joint session of Congress in 1960.

While some other European leaders have kept a distance from Trump, Macron has worked hard to remain close to the US president. The two leaders speak frequently by phone.

Macron and Trump are also due to discuss Syria less than two weeks after the United States, France and Britain launched air strikes there in retaliation for a suspected chemical weapons attack that killed dozens.

Macron said last week he believed he had persuaded Trump to keep US troops in Syria, though Trump has been insistent on bringing them home.