WASHINGTON, United States (AFP) — Donald Trump warmly welcomed German Chancellor Angela Merkel at the White House Friday for talks the US president said would focus on Iran, international trade and military ties.

Merkel arrives facing an uphill struggle to save the Iran nuclear deal, avoid a trade war and make her relationship with the US president functional again.

The German leader’s visit has already been overshadowed by a backslapping three-day festival of “fraternite” between Donald Trump and French President Emmanuel Macron this week.

Aware of the optics, anxious German diplomats pressed — in vain — for Merkel to enjoy a similarly meaty two days at the White House, betting the face time would help sweeten difficult relations, officials told AFP.

But the visit got off to a surprisingly warm start, and the body language showed. The two leaders exchanged kisses on the cheek as Merkel emerged from her limousine, and Trump then praised her as “an extraordinary woman” as they sat together in the Oval Office.

“We actually have had a great relationship right from the beginning but some people didn’t understand that,” Trump told reporters. “But we understand it, and that’s what’s important.”

When Merkel last came to Washington, the cautious dry-witted chancellor held several awkward joint appearances with her more impulsive host — clashing publicly over defence spending, trade and migration.

This time around, the tricolour French flags were only just removed in time for Merkel’s arrival for a one day, run-of-the-mill “working visit.”

The stylistic differences between the Macron and Merkel visits are “very telling” according to Mona Krewel of Cornell University.

It points, she said, “to the much more difficult relationship Trump has with Merkel.”

That is a dramatic change in fortunes for the German leader who, for more than a decade, was seen by Washington not just as a sensible and pragmatic interlocutor, but the de facto leader of Europe.

Her relationship with Barack Obama was particularly close, officials from that administration have said, so much so that he was a powerful voice encouraging her to run for a fourth term.

Their partnership has proven — along with centrists claiming her as the new “leader of the free world” — to be a poisoned chalice for Berlin in the age of Trump.

Just hours before the chancellor landed late Thursday, some 15 months after Trump was sworn into office, the Republican-controlled Congress finally got around to confirming an ambassador to Germany.

Shortly after his nomination, Richard Grenell — who is known for his pugilistic conservatism and combative defence of Trump’s “America First” policies — told AFP it was “humbling” to be chosen for a post once held by John Quincy Adams, and he vowed to work diligently.

“There is a special responsibility that all US officials have to reject partisan politics when they take government service jobs,” he said.

Merkel this week stressed that, despite the differences, she wants to “cherish and nurture” the bedrock transatlantic alliance.

Sitting next to Trump Friday, she said her mission to Washington — just weeks after her swearing in for a fourth term as Germany’s leader — will “underline that we wish to deepen our relationship further.”

Despite her more sober style, she is unlikely to diverge much from Macron on substance.

She will be trying to persuade Trump to back off his dual threats of punitive metal tariffs that could spark a transatlantic trade war and his instinct to scrap the Iran nuclear deal.

Trump last month announced tariffs of 25 per cent on steel and 10 per cent on aluminium, claiming foreign imports were harming US national security by undermining the domestic production needed for military readiness.

After an outcry from US allies, he granted a temporary exemption to key partners including the European Union — but this expires on May 1.

Trump’s National Economic Council Director Larry Kudlow told CNBC Thursday that Washington would continue to exempt allied economies, including the EU, if they make concessions, citing the example of “equal treatment of automobiles.”

Trump also signalled the two could discuss rapidly-moving progress on the Korean peninsula, where leaders from North and South Korea held a historic summit. Trump said he has spoken “quite a bit” with Merkel about what he called “the North Korean problem.”

The next looming deadline regarding Iran is May 12, the date by which Trump has threatened to tear up the landmark 2015 agreement to stop Iran from developing nuclear weapons in return for relief from international sanctions.

Trump has called the agreement, which Germany helped negotiate, “insane,” demanding that its “disastrous flaws” be fixed.

Macron came away from his meetings speculating that Trump would kill the deal, but debate continues to rage.

US Secretary of Defence Jim Mattis on Thursday said Washington was yet to make “any decision” on tearing up the deal, but stressed that some aspects needed to be improved.

It is unclear how Mike Pompeo’s confirmation as secretary of state will tilt the debate.

Despite his hawkish views on Iran, his criticism of the deal had been somewhat tempered in internal discussions, officials said.

The German foreign ministry has insisted that “the biggest priority is maintaining the existing nuclear accord.”