The President of the European Council dismissed Mr Trump’s leadership a “seasonal turbulence” and predicted the G7 group would prevail despite America’s isolationist policies.
And he warned it was now the US, and not “usual suspects” such as Russia, which posed the biggest threat to the current, Western-led international order.
Speaking ahead of the two-day event in Canada today, Mr Tusk said this year’s summit would be “even more challenging” than 2017’s – an event which he had previously billed as the most difficult in years.
He warned it is “evident” that Mr Trump and the rest of the G7 were at loggerheads over trade, climate change and the Iran nuclear deal.
And he went on to further warn that the United States, under Mr Trump’s presidency, now posed the biggest challenge to West’s continued leadership on the global stage.
He said: “Naturally we can not force the US to change their minds. At the same time we will not stop trying to convince our American friends, and President Trump, that undermining this order makes no sense at all, because it would only play into the hands of those who seek a new post-West order, where liberal democracy and fundamental freedoms would cease to exist.
“This is in the interest of nether the US nor Europe.”
He said “on most fronts”, the G7 was united in its efforts, including countering the aggressive stance of Russia, securing denuclearisation on the Korean Peninsula and finding a way to end the long-running Syrian civil war.
He added: “Our unity in these areas is crucial for Europe and the whole world.
“And I still believe that the overall unity of our group will prevail.
“Despite seasonal turbulences, we will persevere. I have no doubt about it.”
World leaders from the G7 are preparing to meet in Canada for a major two-day summit.
Mr Trump is expected to face stern opposition from the majority of the group over his protectionist policies on trade, including harsh new tariffs on steel and aluminium which would hit the European Union and Canada.
Before leaving Washington this morning, Mr Trump caused fresh controversy by suggesting Russia should be invited back into the G7, to reform the G8, after Vladimir Putin was kicked out in 2014 after his annexation of Crimea.
But the US President recommended Russia be re-invited into the club, insisting Moscow should have a seat at the table.
The UK was quick to hit back at Mr Trump’s suggestion, insisting Russia must “change its approach” before even being considered for membership.
A senior Government source said: “The PM has always said we should engage with Russia but beware.
“We should remind ourselves why the G8 became the G7 – it was after Russia illegally annexed Crimea.
“Since then we have seen malign activity from Russia in a whole variety of ways, including on the streets of Salisbury in the UK.
“Before any conversations can take place about Russia rejoining, it needs to change its approach.”