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.”

Asked about Russian president Vladimir Putin's role in the crisis, McCain said: “There's no doubt that Ukraine is of vital importance to Putin. I think it was [Henry] Kissinger, I'm not sure, said that Russia, without Ukraine it's an eastern power, with Ukraine it's a western power. This is the beginning of Russia, right here in Kiev. So Putin views it as most highly important and he has put pressure on Ukrainians – the price of energy, different kinds of activities. The word is very clear that he has made certain threats. Whether he would carry them through I don't know.”

“He's put pressure on Moldova, Lithuania, Estonia, Latvia – all of the so-called 'near-abroad'. And of course Ukraine is the crown jewel.”

Asked by CNN host Candy Crowley whether now was a good time to be be “taking Russia on”, given US diplomatic co-operation with Russia on issues such as Iran's nuclear programme and the civil war in Syria, McCain said: “I don't think we would be 'taking on Russia'.

“These people love the United States of America, they love freedom – and I don't think you could view this as anything other than our traditional support for people who want free and democratic society.”