Major EU countries are ready to provide defence and financial aid to Ukraine if the United States reduces support, Polish Foreign Minister Radoslaw Sikorski said on Tuesday.

He was speaking on the 1,000th day of the Russian invasion of neighbouring Ukraine, as foreign ministers from six major European countries held talks in Warsaw dominated by the war and Donald Trump's return to power.

Top diplomats from France, Germany, Italy and Poland joined the meeting, while Britain's David Lammy and Spain's Jose Manuel Albares took part by video.

"I note with appreciation the readiness of the largest European Union countries to assume the burden of military and financial support for Ukraine in the context of a possible reduction in US involvement," Sikorski told reporters after the talks.

The Warsaw gathering followed a meeting of all EU foreign ministers in Brussels and comes as Trump's return to the White House threatens a drastic change in US policy nearly three years into the Russian attack on Ukraine. (AFP)