"If article nine of the Vienna Conventions … is applied in regard to the Russian ambassador, it will not stand without a corresponding reaction from the Russian side," a foreign ministry source told news agency Interfax.

Relations between Russia and Ukraine are already strained by a squabble over gas transit in January that led Moscow to cut supplies and caused several European countries to be deprived of gas for two weeks.

The latest row between appears to have been sparked over an interview Ambassador Viktor Chernomyrdin gave to a Russian newspaper last week, in which he compared the country’s leadership to a pair of dogs.

"It is impossible to come to an agreement on anything with the Ukrainian leadership. If different people come in, we’ll see," Chernomyrdin, a former Russian prime minister, told tabloid daily Komsomolskaya Pravda on 11 February.

Ukrainian President Viktor Yushchenko’s office has repeatedly protested that the deal agreed by his arch-rival Prime Minister Yulia Tymoshenko and her Russian counterpart Vladimir Putin was a sellout for Ukraine.

Chernomyrdin said that the leaders of the Ukrainian state are always "at each other like dogs, slamming one another. She signed what was needed for Ukraine and now he’s shooting holes in it: where’s the money?"

Ukraine’s foreign ministry said Tuesday it had summoned Chernomyrdin and warned him over what it called "unfriendly comments", without being specific about the incident.

Ukrainian Foreign Minister Volodymyr Ogryzko told Chernomyrdin he was displeased with "unfriendly comments" he made about Ukraine and its leaders, a ministry statement said.

Flamboyant right-wing Russian politician Vladimir Zhirinovsky accused Ukraine’s president of orchestrating the row in order to bolster his chances in upcoming elections.

"He is the ambassador of our country and threats of expulsion against an ambassador can only be made in the event of the beginning of a war between two governments," Zhirinovsky said.

"Of course there won’t be a war, but the actions of the president of Ukraine were done to strain relations because he has no possibility of winning the elections," he said.

The Ukrainian ministry said it could draw on rules governing diplomatic relations to declare Chernomyrdin "persona non grata" over the row, which could further destabilise Kiev-Moscow relations.

[AFP / Expatica]