The political climate in Ukraine remains tense, with opposition leader Viktor Yushchenko calling on his supporters to renew their blockade of government headquarters

The call came after Prime Minister and defeated presidential rival Vicktor Yanukovich announced he would return to his official ministerial offices after a one-month absence and chair a cabinet meeting.

The opposition leader says he fears the government may try to steal budget funds or state assets in its last days.

Speaking to tens of thousands of his supporters in Kiev, he said “In what country is it possible for a government that has been dismissed to say that it doesn’t want to go? No meeting of an illegitimate government can take place.”

On Tuesday Mr Yushchenko was provisionally declared the winner with 52 per cent of the vote against 44 per cent for Mr Yanukovich, a winning margin of more than two million votes.

But the pro-Moscow Mr Yanukovich, who refuses to concede defeat and plans to appeal to the courts, seems determined to show he still holds considerable power.

For his part, Mr Yushchenko appears equally determined to demonstrate he has the authority to eject his rival from office.

But Mr Yanukovich, who may emerge as Ukraine’s main opposition leader to the new administration, is beginning to look isolated, with out-going President Leonid Kuchma refusing to offer his support.

But he received some comfort from Russia’s foreign ministry.

On Tuesday it criticised the Organisation for Security and Co-operation in Europe, which monitored the election, for playing down what the Kremlin thought were “widespread” voting violations on December 26.

The United States is urging Ukraine’s courts to uphold Mr Yushchenko’s election victory.

In the run up to Sunday’s p0ll, the US was criticised by both Russia and Mr Yanukovich for seeking to influence the outcome after the first, disputed runoff election.

While State Department spokesman Adam Ereli avoided congratulating Mr Yushchenko, he made clear Washington believes Yushchenko, who wants to align the former Soviet state with the West, won fairly.

“We would expect that they (the judicial authorities) would conduct a fair, transparent and legal review that results in an outcome that reflects the will of the Ukrainian people,” he said.

Meanwhile, Mr Yushchenko’s top associates were jostling for position of prime minister.

Followers of Yulia Tymoshenko, a firebrand who inspired the huge pro-Yushchenko crowds during weeks of street protests in freezing weather, claim she has a strong case.

However, Mr Yushchenko, whose Our Ukraine is the largest party in the opposition coalition, is thought to prefer to keep power in his own grouping.

His party is not short of would-be prime ministers, notably Petro Poroshenko, a businessman and head of the parliamentary budget committee.