Ukraine PM vows fight

"Ukraine is and will be part of the Western world," the transitional premier of Ukraine, Arseniy Yatsenyuk, told reporters at the White House on Wednesday.

Speaking alongside US President Barack Obama, Yatsenyuk vowed that his country would continue pursuing its plan for closer ties with the EU and would not buckle under pressure from Moscow.

Ukraine will "never surrender," he said.

US President Barack Obama reiterated Washington's support for Kyiv, saying: "We will stand with Ukraine."

Earlier on Wednesday, the G7 industrial nations jointly warned Russia to "cease all efforts to change the status of Crimea" or face "further action, individually and collectively."

The interim government in Kyiv finds itself not only trying to stabilize a country politically divided after several months of popular protests, but also attempting to deescalate tensions with Russia.

Last month, Moscow deployed thousands of soldiers to Ukraine's southern Crimean peninsula. Russian President Vladimir Putin has said he was answering calls for help from ethnic Russians who believe they are threatened by EU supporters in Ukraine. Moscow does not recognize the legitimacy of Ukraine's transitional government.

Referendum due Sunday

The shakiness of Crimea's allegiance to Kyiv has also worried Ukraine's interim government. Voters in the Black Sea peninsula are preparing for a March 16 referendum, which could see them become part of the Russian Federation.

Western leaders have accused Russian Vladimir Putin of stoking ethnic tensions for his own gain in the majority Russian-speaking territory. Minority ethnic groups - some of whom were persecuted by Russia in the past - have said they want to remain part of Ukraine and say the referendum is not legitimate.

Moscow has declined offers from the US and the EU to negotiate a diplomatic solution via a contact group, comprised of representatives from Ukraine, the EU and the US.

On Wednesday, President Obama vowed more sanctions against Russia if it continued its current course, echoing warnings earlier in the day from the G7 and German Chancellor Angela Merkel.

If Russia does not comply, the US will be "forced to apply costs" to Moscow, Obama said, adding that Washington would not recognize "any referendum that goes forward."

US releases oil from strategic reserve

The meeting between Obama and Yatsenyuk came shortly after the US Energy Department announced it would release five million barrels of oil from its Strategic Petroleum Reserve.

Citing "significant changes in the system," the Energy Department said it was conducting a long-planned test. It denied suggestions that the decision was meant as a warning to Russia, which is a major world supplier of oil and natural gas.

Putin talks with Crimea and France

Russian President Putin continued his telephone diplomacy on Wednesday, speaking to both the French president and the leader of a Crimean ethnic minority.

According to the office of the French presidency, Russian officials would meet with French foreign and defense ministers on March 18 "if there is progress in the Ukraine case."

That encounter would be held at the two nations' annual security meeting, which they agreed to in 2002.

Putin also spoke with the leader of Crimea's Muslim Tatar minority, Mustafa Dzhemilev. The group wants to remain part of Ukraine.

"I expressed doubts over the decision to organize a referendum and its legitimacy," Dzhemilev told Ukrainian Kanal 5 television.

The Russian media confirmed reports of the conversation, but gave no detail as to Putin's response.

kms/ipj (AP, AFP, Reuters, dpa)