Ukrainian Prime Minister Yulia Tymoshenko was delayed flying to talks in Moscow on Thursday when President Viktor Yushchenko, her estranged political ally, commandeered her plane, she told reporters.

Tymoshenko told journalists accompanying her on the trip that Yushchenko had taken over her aircraft without warning and used it for his own trip to western Ukraine.

Tymoshenko was due in Moscow to discuss the thorny issue of Russian natural gas prices for 2009.

The reporters said government officials had found a charter aircraft and she had taken off for Moscow with a small delay.

Yushchenko's press service said a plane taking him to the western city of Lviv had developed technical difficulties and returned to Kiev, where he had taken a "reserve" plane.

It gave no indication that the aircraft had originally been designated for Tymoshenko.

Yushchenko and Tymoshenko were allies during the 2004 "Orange Revolution" that brought the pro-Western president to power, but have since been constantly at loggerheads.

The latest coalition underpinning her government collapsed last month after Yushchenko's allies walked out. Unless a new coalition is put in place this month, the ex-Soviet state will face its third election in as many years.