In a letter addressed to Biden seen by AFP Thursday, Kosovo's President Vjosa Osmani warned against Moscow's efforts to "destabilise" the Balkans.

"Kosovo's membership in NATO has become imperative", Osmani wrote.

"We express our hope and expectation that the United States will use its leadership and influence to actively support and advance the complex NATO membership process for Kosovo."

The letter was sent to the White House last week.

Kosovo's Prime Minister Albin Kurti already pressed a case for EU and NATO membership, telling AFP that Russia's invasion of Ukraine meant that both organisations needed to make it easier -- and faster -- for candidates to join.

"As they will target new conflicts, the Western Balkans in general and Kosovo in particular are at risk," Kurti warned.

Moscow has been a fierce opponent of Kosovo since the war in the 1990s when Russia's longtime ally Serbia saw its security forces pushed out of the territory with the crucial help of NATO air strikes.

Ethnic-majority Albanian Kosovo proclaimed independence from Serbia in 2008, a move that several countries, including Russia and Ukraine, have refused to recognise.

Russia wields veto power at the United Nations that has helped block formal recognition of Kosovo.

Following Russia's invasion of Ukraine on February 24, Kosovo launched its own targeted sanctions against Moscow.

It has also pledged to welcome thousands of Ukrainian refugees and allocate a special fund to assist the Ukrainian people.