Former Prime Minister Mikhail Kasyanov speaks at a news conference in Moscow (File)

Russia's Supreme Court has upheld the Central Electoral Commission's decision that barred former Prime Minister Mikhail Kasyanov from the upcoming presidential election.

The court Tuesday declared that Mr. Kasyanov's exclusion from the March 2 vote is valid.

The electoral commission barred Mr. Kasyanov on the grounds that tens of thousands of signatures on his nominating petitions were invalid. Supporters of the former prime minister say the ban is a Kremlin ploy aimed at protecting favored candidate Dmitri Medvedev from serious challengers.

In a related development, Russia says it has offered concessions to Europe's top vote-monitoring organization, in response to European concerns about restrictions on the timing and size of its observer mission. The compromise, offered to the elections arm of the Organization for Security and Cooperation in Europe, says monitors can start work February 20, instead of February 28 as earlier decreed.

European monitoring officials have not responded publicly to the new offer.

Last week, Russia invited fewer observers than in past years to monitor the polls. The invitation followed Russian Foreign Ministry accusations that the OSCE is trying to sabotage the March 2 vote.

Some information for this report was provided by AFP and AP.