Trump speaks often of his respect for, and friendship with, China's President Xi Jinping
Trump speaks often of his respect for, and friendship with, China's President Xi Jinping AFP / Brendan Smialowski

President Donald Trump on Tuesday gave a foretaste of his convention-wrecking diplomacy at next weekend's G7 by calling for Russia -- expelled from the group of democracies -- to be readmitted.

Coming four days before he arrives at the summit in the French seaside resort of Biarritz, Trump's support for President Vladimir Putin was likely to be only the first diplomatic hand grenade unleashed on what used to be a cozy club of rich, Western allies.

"I could certainly" support that, he told reporters at the White House. "It's much more appropriate to have Russia in. It should be the G8, because a lot of the things we talk about have to do with Russia."

Russia was kicked out of the old G8 format after the 2014 invasion and annexation of Crimea, in Ukraine. Putin has also been accused of orchestrating murders of opponents in Britain and elsewhere in Europe, as well as attempting to manipulate the 2016 US election that saw Trump win a surprise victory.

But Trump, in comments that may irk G7 partners meeting from Saturday on the French Atlantic coast, declared that Russia had been expelled because his predecessor Barack Obama had been "outsmarted" by Putin.

Bracing for drama

Annual Group of Seven summits -- bringing together the leaders of Britain, Canada, France, Germany, Italy, Japan and the United States -- were typically non-confrontational affairs.

Until Trump.

At the G7 in Quebec last year, he exploded proceedings and left in a fury, engaging in personal insults over trade with Canadian Prime Minister Justin Trudeau and refusing to sign the collective final statement.

G7 leaders better buckle up again, warns Robert Guttman, director of the Center for Politics & Foreign Relations at Johns Hopkins University.

"He's going to be a bull in a china shop," Guttman said.

The French hosts hope they can better manage Trump this time. In particular, a French diplomat told reporters, the traditional importance of the final communique will be de-emphasized.

That's "one way to avoid the situation we had in Canada last year."

Is America 'winning?'

But French President Emmanuel Macron wants the G7 to talk about tackling global inequality.

That's a topic ill-suited to Trump's fiercely America-centric -- critics say isolationist -- worldview ahead of elections next year.

As Trump likes to tell rallies amid chants of "USA, USA," the only metric he cares about on the world stage is whether America is "winning."

Nowhere is this clearer than on climate change -- a major factor, according to France, in driving economic and social inequality.

Trump pulled the United States out of the 2015 Paris climate accord on reducing carbon emissions and he remains proudly defiant over what allies saw as his abandonment of an attempt, literally, to save the world.

Guttman says Trump won't care what the other G7 partners think. His hardcore voter base is his target audience.

"Trump comes not as a statesman, but as a politician fighting very hard for reelection."

'Reassertion'

James Roberts, at the conservative Heritage Foundation, says Trump is merely correcting what Republicans consider to have been the foreign policy drift under his Democratic predecessor Barack Obama.

"It's a reassertion of American resolve," Roberts said.

Trump will push back on France's digital tax, imposed to plug what Macron's government says is a massive loophole in which US companies like Google operate abroad while paying almost nothing.

Branding this "foolishness," Trump has threatened to retaliate with tariffs on French wine imports.

G7 leaders, especially Germany's Angela Merkel, can also expect pressure over financial contributions to NATO, the bedrock of trans-Atlantic security that Trump says relies too heavily on US largesse.

And the six partners will struggle to get flexibility from Trump on other contentious points: Washington's aggressive posture against Iran, and the roller coaster trade war with China that is contributing to jitters over a possible global economic recession.

Don't shoot the messenger?

There will at least be one new friend in the room.

Freshly installed Prime Minister Boris Johnson is eager for US support as he pushes Britain through what could be a perilous no-deal Brexit.

Trump has dangled the prospect of a big bilateral trade agreement and the White House will continue using that as bait to try and force Britain into shutting out Chinese company Huawei from the 5G market.

On Tuesday he again praised Johnson, saying he'd be "fantastic."

As Macron and Japanese Prime Minister Shinzo Abe have discovered, strong personal ties with Trump don't necessarily result in an easy friendship.

But Roberts says that strategic challenges from China and Russia mean the G7 partners are going to have to put up with Trump whether they want to or not.

"They don't like President Trump's style but you can't change the facts because you don't like the messenger," Roberts said. The European Union is "not a superpower and it still has to rely on the United States."

There will be no escaping Trump for long: it's his turn to host the G7 in 2020.