LONDON/BRUSSELS (REUTERS) - Mr Boris Johnson is about to feel the pinch of Brexit Britain's new global status: Squeezed on one side by Europeans in no mood to yield, and on the other by a United States driving a hard bargain for its economic support.

With a deepening political crisis at home, Mr Johnson makes his international debut at a gathering of Group of Seven leaders in the French resort of Biarritz on Saturday (Aug 24), less than three months before the United Kingdom is due to leave the European Union.

With no sign of an exit deal being agreed by then, the world's fifth-largest economy is on course for a messy divorce from its biggest trading partner and looking across the Atlantic to US President Donald Trump for a new trade deal and support.

The three-day meeting in south-west France will lay bare the new realities for Britain: collapsing influence in Europe and growing dependency on the US. Neither is a comfortable position for New York-born Johnson, who took office with a swagger last month promising Brexit by Oct 31 no matter what.

"The UK risks being stuck uncomfortably between a United States it disagrees with and a Europe it will struggle to influence," said Mr Thomas Raines, head of the Europe Programme at London-based think tank Chatham House.

Ever since World War II, Britain has tried to temper Europe's drive for integration with a so-called special relationship with the US. Brexit forces a departure from that strategy.

Britain's exit from the EU is not on the agenda for the meeting, attended by the leaders of the US, Britain, France, Germany, Italy, Canada, Japan and the EU, but is expected to feature heavily in discussions on its sidelines.

With Mr Johnson insisting on re-opening a previously negotiated exit agreement that the British Parliament rejected three times and that Brussels says cannot be reopened, a no-deal Brexit is seen as an increasingly likely outcome.

Both sides say they do not want it to happen, but will be prepared for that outcome. The EU insists Britain will be hit hardest and leaked British government "worst case" planning documents show possible food, fuel, and medicine shortages.

UK-EU 'ICE AGE'

Short-term disruption aside, Mr Guntram Wolff, director of the Brussels-based think-tank Bruegel, said the long-term implications could be even more damaging, isolating Britain from its closest neighbour.

"The real danger of a no-deal Brexit... is the political implications, and for a long while there will be an ice age between the EU and the UK," Mr Wolff said.

"Then Trump says (to the UK), 'I'm your buddy' - and potentially drives a wedge between the EU and the UK."

Ahead of the G-7 meeting Mr Johnson travels to Berlin and Paris, having failed to break the impasse with a letter to EU Council President Donald Tusk.

British government sources said they did not expect a breakthrough this week, or at the G-7.

"In Biarritz, the EU side will hold its ground on Brexit," said one EU official dealing with Brexit. "We don't expect much to be agreed on Brexit there, even if some interesting exchanges may take place."

EU sources said Brussels was instead waiting to see if Britain's Parliament, where a small majority is also opposed to leaving the bloc without a deal, could force Mr Johnson into delaying or halting the exit process.

US ALIGNMENT

In contrast, Mr Johnson's pre-summit phone call on Monday with Mr Trump prompted an enthusiastic response from the US leader on Twitter: "Great discussion with Prime Minister @BorisJohnson today.

"We talked about Brexit and how we can move rapidly on a US-UK free trade deal. I look forward to meeting with Boris this weekend, at the @G7, in France!"

Earlier this month, senior Trump aide John Bolton visited London carrying a message from his boss that the US would set aside foreign policy differences and focus on doing whatever it could to help Britain through the Brexit process.

But, even though Mr Johnson and other pro-Brexit advocates argue that the US will be a crucial ally for a Britain unshackled from EU trade policy, Mr Trump's support is likely to come at a price.

Britain has long been the US' closest military ally, but its status as an influential player in the EU has also given it clout to diverge from Washington when it disagrees - something it has frequently done since Mr Trump came to power.

"At the point at which it is leaving the EU, it finds itself much closer to the European position on most big issues than to the Trump administration: on climate change, on international trade, on the Iran (nuclear) deal," Mr Raines said.

That leaves Mr Johnson caught between European and American thinking. He will need to avoid angering a volatile Mr Trump and risking trade ties, but also to be wary of alienating himself from other leaders who have a more multilateral approach to world politics.

"Boris should not attempt to corral his fellow heads of government into a common line on every issue, nor set himself up as the go-between for the US and Europe," former British foreign minister William Hague wrote in the Telegraph newspaper.

"Such efforts would be doomed to fail, for now at least, and more likely to end in ridicule than renown."