"Nothing has changed since March, 2014, when Russia's participation in the G8 was stopped. Ukrainian Crimea is being occupied as before, Ukrainian Donbas is suffering from war," Ukraine's President Volodymyr Zelenskiy said.

But Germany, France, Britain — all G7 members — quickly rebuffed Trump, noting that Russia was excluded after it annexed Ukraine's Crimea and then backed an anti-Kiev rebellion in the industrial region of Donbas in eastern Ukraine.

U.S. President Donald Trump said on Tuesday it would be "appropriate" to have Russia rejoin what used to be the G8. France will host a meeting of G7 leaders this weekend.

Ukraine's president backed leading European powers on Thursday in opposing the readmission of Russia to the Group of Seven advanced economies, saying Moscow still occupied Crimea and was frustrating peace in eastern Ukraine.

Echoing that view, a European Union official said readmitting Russian President Vladimir Putin to the group without conditions would be "counterproductive, a sign of weakness."

"The EU remains strongly of the view that the reasons for Russia's exclusion in 2014 from the then-G8 are still valid today as they were valid five years ago. So the EU will be against the idea of reinviting Russia to G7," he said.

The EU and the United States have imposed sanctions on Russia over its role in the Ukraine conflict, in which some 13,000 people have been killed to date, according to U.N. data. Fighting continues in Donbas, albeit at a low intensity.

A peace process brokered by Berlin and Paris has stalled.

Speaking in Berlin on Wednesday, Britain's new prime minister, Boris Johnson, also cited the poisoning of a former Russian double agent in England last year as a reason not to readmit Russia to the G7.

Britain and the EU blamed Russia for that attack. The Kremlin denied any involvement.

Zelenskiy thanked Johnson in a telephone call for supporting Ukraine's sovereignty, the Ukrainian president's office said on Thursday.

The disagreement over how to handle Russia - where Trump has praised Putin despite Western criticism of his record — is just one of several areas of tension in trans-Atlantic ties that will be on display at the G7 gathering in France.

The G7 groups the United States, Japan, Germany, Britain, France, Italy and Canada.