Senator John McCain on Sunday told thousands of Ukrainian protesters camped on Kiev's main square that Ukraine's destiny lay in Europe and that it would make Europe better.

"Ukraine will make Europe better and Europe will make Ukraine better," he said to crowds protesting against President Viktor Yanukovich's U-turn in trade policy away from Europe towards Russia.

"We are here to support your just cause, the sovereign right of Ukraine to determine its own destiny freely and independently. And the destiny you seek lies in Europe," said McCain, a leading Republican voice on US foreign policy.

The presence of McCain at the anti-government rally after a weeks-long stand-off between demonstrators and the authorities further highlighted the geo-political East-West tug-of-war which Ukraine is once again at the centre of. Politicians from Berlin and Brussels have paid morale-boosting trips to the square, drawing denunciation from the Russian prime minister, Dmitry Medvedev, for "crude" meddling in Ukraine's affairs.

McCain is in Ukraine with a Connecticut Democrat, Senator Chris Murphy.

Speaking to CNN on Sunday, McCain said: “What we're trying to do is try to bring about a peaceful transition here, that would stop the violence and give the Ukrainian people what they unfortunately have not had, with different revolutions that have taken place – a real society. This is a grassroots revolution here – it's been peaceful except when the government tried to crack down on them, and the government hasn't tried that since.

“I'm praising their ability and their desire to demonstrate peacefully for change that I think they deserve.”