Ukraine's newly-inaugurated President, Mr Viktor Yushchenko, named radical ally Yulia Tymoshenko acting prime minister today, a statement said.
The statement, which appeared on Yushchenko's official website, said the president had issued a decree on the appointment before leaving on a one-day trip to Moscow. The nomination must secure parliamentary approval.
Mr Yushchenko flies to Moscow today to tell Russian President Vladimir Putin about his plans for steering the country towards the West. Russian commentators expect Mr Putin to question Mr Yushchenko over his economic and foreign policy plans.
Mr Yushenko defeated the pro-Russia candidate Mr Viktor Yanukovich in an re-run election after the original ballot was declared void amid charges of electoral fraud and intimidation.
But he has made Moscow his first foreign visit and is expected to try to assure Mr Putin that that Russia remains and important strategic partner, despite his intention to build stronger links with Western Europe.
The Ukrainian president is to tour western and central Europe later in the week, but the country relies heavily on Russian energy supplies, meaning it cannot afford to sever its Russian links.
The Kremlin will be keen to discover whether Mr Yushchenko is interested in the Putin-supported loose economic bloc with Russia and ex-Soviet states Belarus and Kazakhstan.
Mr Yushchenko will be seeking assurances that Russia will not stir unrest in the Russian-speaking east of Ukraine - the power base of Mr Yanukovich.
The Russians will be aware that the new president yesterday told supporters in Kiev's Independence Square made no of mention of Russia in his speech after taking the oath of office.
"Our way to the future is the way of a united Europe. We, along with the people of Europe, belong to one civilisation. We share similar values," he told the crowd.