Donald Trump's high-stakes trip to Europe, where he faces a prickly G20 meeting and animosity from traditional US allies, kicks off on a comforting note Thursday -- in front of a friendly crowd bussed in by his sympathetic Polish hosts.

Air Force One touched down in Warsaw late Wednesday, for what is the US president's second foreign outing after a European tour in May that exposed fierce mistrust.

The US president's four-day swing starts in Warsaw, where he will deliver a major speech, before moving on to the northern German city of Hamburg for his first G20 summit, where tricky geopolitical currents -- from rumbling transatlantic discord to increasingly difficult ties with China -- will converge.

Looming large over the entire visit is Pyongyang's test of an intercontinental ballistic missile that could deliver a nuclear payload to Alaska.

Tough-talking Trump had previously vowed North Korea would not be allowed to possess an ICBM, and leaders from rival and allied powers alike will be watching closely to see whether his threats were bluster or will crystallise into action.

After repeatedly urging Beijing to ratchet up the pressure on North Korea, Trump will hold what promises to be a testy meeting with Chinese President Xi Jinping in Hamburg to trace the next steps.

"Trade between China and North Korea grew almost 40% in the first quarter. So much for China working with us - but we had to give it a try!" Trump tweeted indignantly on Wednesday.

- 'Fake news' -

On Friday, Trump will hold a meeting with Russian President Vladimir Putin that will -- amongst other things -- be pored over for its significance to US domestic politics.

Several of Trump's closest aides are under investigation for possible ties with Moscow, which US intelligence agencies say tried to tilt the election in the Republican candidate's favour.

The scandal continues to eat away at his administration, with key White House staff being forced to hire their own lawyers and spend time rebuffing new allegations.

So far, Trump has been reluctant to acknowledge Russian interference in the election or criticise the veteran Russian leader and has branded allegations against his aides as "fake news".

Even simple photographs of Putin and Trump shaking hands or meeting face-to-face pose a political risk for the US president and will likely be weaponised by his foes in the United States.

- 'Disastrous trip to Brussels' -

Trump will look to a public speech Thursday to burnish his credentials as a global statesman and deflect criticism that he invited ridicule on the United States after an acrimonious G7 summit during his first trip overseas in May.

In Poland, Trump has a willing host in the form of President Andrzej Duda, whose rightwing politics resemble his own.

Trump will take the stage at Warsaw's historic Krasinski Square, with organisers expecting thousands -- perhaps tens of thousands -- to attend, many arriving on free buses laid on by Poland's ruling party.

"It is important that President Trump feel good about his visit to Poland," Stanislaw Pieta, a member of parliament for the Party of Law and Justice told the AFP.

That should provide welcome relief from the cool reception he is likely to receive elsewhere.

"After his disastrous trip to Brussels and Taormina, friendly pictures with European leaders and cheering crowds at his public speech could help Trump repair his image at home," said Piotr Buras of the European Council on Foreign Relations.

During the speech at Krasinski Square -- which memorialises the Warsaw uprising against Nazi occupation -- Trump "will lay out a vision, not only for America's future relationship with Europe, but the future of our transatlantic alliance and what that means for American security and American prosperity," said national security adviser HR McMaster.

While Warsaw may be the least barbed part of the trip, it is not without its own difficulties as Poles watch closely to see if Trump's reluctantly professed commitment to European security can be relied upon.

Poland, like many countries in eastern and central Europe, sees NATO and its mutual defence pact as a major deterrent to Russian adventurism and a guarantee of hard-won independence.

Trump has professed to favour the alliance's one-for-all-all-for-one commitment, but in the same breath has trashed European allies for not spending enough to defend themselves.

In public, European officials say the decades-old transatlantic partnership is inviolable and essential.

In private, they wonder whether it can survive four or eight years with Trump at the helm.

source: AFP