The shock waves from the Russian invasion of Georgia sparked a new crisis in Ukraine yesterday as the pro-Western Orange coalition fell apart in acrimony.

President Yushchenko accused his former ally, the Prime Minister Yuliya Tymoshenko, of forging a pro-Russian alliance to curtail his powers, claiming that a coup was under way a day before Dick Cheney, the US Vice-President, was due to visit Kiev, the Ukrainian capital.

Mrs Tymoshenko countered with the allegation that the President had destroyed the Government himself after deputies from his party withdrew from her ruling coalition. Mr Yushchenko threatened to call a snap election unless a new coalition was formed within 30 days.

The crisis erupted after parliament passed new laws restricting the powers of the President and making it easier to impeach him. The Tymoshenko Bloc voted for the legislation with the Party of Regions, the pro-Moscow Opposition led by Viktor Yanukovych, the former Prime Minister Members of the President’s Our Ukraine party then left Mrs Tymoshenko’s coalition Government, which was formed after elections that ended a similar political crisis 12 months ago.

In an address on national television Mr Yushchenko said: “A political and constitutional coup d’état has started in the parliament.”

He appeared to accuse Moscow of interference, saying: “The Tymoshenko Bloc has accepted union with the Regions Party and the Communists. The basis of this formation is not Ukrainian, I underline not Ukrainian.”

Vyacheslav Kirilenko, the leader of Our Ukraine, described the Party of Regions and the Tymoshenko Bloc as a “pro-Kremlin majority”. He said that the legislation was “just what the Kremlin has been asking certain political forces to do”.

Mr Yushchenko and Mrs Tymoshenko led the Orange Revolution in 2004 that swept their pro-Western coalition to power after a popular revolt against a rigged presidential election in favour of Mr Yanukovych.

Both want to take the country into Nato and the European Union, but repeated conflicts between them have paralysed Ukrainian politics for long periods. Russia bitterly opposes Ukraine’s membership of Nato.

The crisis in Georgia has contributed to Ukraine’s political turmoil. Mr Yushchenko accused Mrs Tymoshenko of “high treason” in allegedly siding with Russia over the war.

She denied the claim, but her party refused to back a parliamentary motion from Our Ukraine that condemned Russia. Mr Yushchenko openly supported Georgia and told The Times last month that Nato membership was “the only way for our country to protect our national security and sovereignty”.

Mr Cheney arrived in Azerbaijan yesterday as part of a tour of former Soviet republics to assert America’s continued commitment to the region. He is due to visit Georgia today in a show of support for President Saakashvili before travelling to Kiev for talks with Mr Yushchenko.

On the eve of his arrival in Tbilisi the US announced $1 billion (£563 million) in aid to Georgia to help to rebuild its war-ravaged economy. US officials said, however, that it was too soon to consider military assistance.

Azerbaijan and Georgia are critical to Western hopes of reducing Europe’s dependence on Russian energy by piping oil and gas from Central Asia via the Caucasus. “President Bush has sent me here with a clear and simple message for the people of Azerbaijan and this entire region: The United States has deep and abiding interests in your well-being and security,” Mr Cheney said after meeting Azerbaijan’s President, Ilham Aliev.

Russia lost 71 soldiers during the war with Georgia, a military prosecutor said. The revised number was seven higher than the previous toll.

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