Kerry, Deshchitsya and British Foreign Secretary William Hague on Wednesday urged Russia to honor the 1994 Budapest Memorandum.

"The Budapest Memorandum sets out the obligations of signatories in return for Ukraine giving up its nuclear weapons," they said in a joint statement during the Paris meetings.

"The Memorandum also obliges the UK, US and Russia to consult in the event of a situation arising where the memorandum commitments are questioned," the statement said.

US President Barack Obama spoke to British Prime Minister David Cameron about Ukraine, the White House said Wednesday.

The two leaders welcomed a military observer mission being undertaken by Organization for Security and Cooperation in Europe (OSCE) at the request of the Ukrainian government, the White House said.

The US and 14 other OSCE states formed the mission Tuesday, intending to monitor the situation in Ukraine's Crimea region. The team planned to leave within 24 hours.

Obama and Cameron also discussed support for the government of Ukraine as it works to stabilize its economy and makes preparations for elections in May, the statement said, adding the leaders agreed to stay in close contact in the days ahead.

Meanwhile, a court in Kiev had issued arrest warrants for the prime minister and parliament speaker of the country's autonomous republic of Crimea, the Prosecutor General's office said Wednesday.

Criminal charges had been brought against them and other Crimean politicians, acting Prosecutor General Oleh Makhnytsky said.

Last Thursday, the regional parliament of Crimea appointed Serhiy Aksyonov, leader of the Russian Unity party, prime minister in a closed session and announced a referendum would be held over the future status of the territory on March 30.

Aksyonov said Saturday he had asked Russian President Vladimir Putin to help ensure peace in the pro-Russian region.

Ukraine crisis talks on course	Putin: Force 'last resort' in Ukraine