France's Macron visits Trump as Iran nuclear deal hangs in balance

* Macron first foreign leader to make state visit under Trump

* Iran says it's "all or nothing" for nuclear deal (Adds Trump quote, return to White House)

By James Oliphant and Marine Pennetier

MOUNT VERNON, Va./WASHINGTON, April 23 (Reuters) - U.S. President Donald Trump and French President Emmanuel Macron emphasized pomp and ceremony on Monday as Macron began a state visit to Washington likely to be dominated by differences with the United States 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 would scrap unless European allies fix by mid-May what he calls "terrible flaws."

"This visit is very important in our current context, with so many uncertainties, troubles and at times threats," Macron said in French remarks 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 program 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," White House spokeswoman Sarah Sanders said.

Macron said on "Fox News Sunday" it would be better to protect the deal instead of getting 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.

CHARM OFFENSIVE

Macron's visit is the first time Trump has hosted a state visit since he took power in January 2017. 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 and his wife, Brigitte, shortly after their arrival at the Blair House residence, took quickly to the streets of Washington, walking past the White House complex to the Lincoln Memorial and greeting tourists.