Kosovo applied to become a member of the Council of Europe Thursday, with officials in Belgrade vowing to prevent Pristina from joining any international organizations and stepping up their anti-recognition campaign.

The application was filed weeks after Russia, a key ally of Serbia, pulled out of the body in March after calls grew for Moscow's expulsion over its invasion of Ukraine.

Being accepted into the continent's top human rights organization requires a two-thirds vote by members, and with Russia not recognizing Kosovo as an independent state, there had been a risk any previous application would fail.

Kosovo says it now has enough backing from the 46-member body to be accepted and the government said it had ordered the foreign ministry to start membership procedures.

Ethnic Albanian-majority Kosovo proclaimed independence from Serbia in 2008. But Serbia as well as its powerful allies China and Russia still do not recognize the move.

Kosovo has incorporated the European Convention on Human Rights, a founding document of the Council of Europe, in its constitution. The Council of Europe, which was set up after World War II to promote human rights, the rule of law and democracy, already has an office in Kosovo to assist with democratic reforms.

"Kosovo is the most democratic country in the (Western Balkans) region," Foreign Minister Donika Gervalla-Schwarz said on her ministry's Facebook page, as she announced the application.

But Serbian President Aleksandar Vucic said his country would "do everything" to oppose Pristina's move in a "peaceful and diplomatic way."

He previously warned Serbia would renew efforts to convince countries that have recognized Kosovo's independence to change their minds.

"In the coming weeks, we will do our best to show that we can fight and preserve our country," he told a local television channel Thursday.

Vucic called for a national security council meeting Friday on the issue.

"There will be no retreat, no surrender in the face of blackmails and ultimatums," he added.

Serbian Foreign Minister Nikola Selakovic also said on Friday that four countries have withdrawn the recognition of Kosovo's independence.

"Through the work of our security services, we have come to the information that at least two large countries are working to support Pristina on new recognitions and to prevent the campaign of withdrawing recognition," he said.

He said that the Government of Serbia and the Ministry of Foreign Affairs would "continue to fight fiercely" and work on withdrawing the recognition of Kosovo.

Gervalla-Schwarz, however, said that Pristina has no information that four countries have withdrawn their recognition of Kosovo.

"We are under pressure to accept the violation of territorial integrity, the violation of international public law, the legal order, to our detriment. The U.S. Government, through a statement from the State Department, issued on the occasion of the first anniversary of the Washington Agreement, made it clear that the U.S. considers the agreement valid and called on Belgrade and Pristina to respect the agreement," Selakovic said.

Kosovo agreed to freeze for a year its efforts to join international organizations, based on the terms of a U.S.-mediated deal in September 2020.

Serbia, for its part, agreed to halt its campaign to persuade countries to revoke their decision to recognize Kosovo's independence.

Tensions between Belgrade and Pristina have remained high since the 1998-1999 war between ethnic Albanian militias and Serbian forces in Kosovo, then a Serbian province stripped of its autonomy.

The conflict left more than 13,000 dead and 1,617 people still missing. NATO’s intervention in the form of a bombing campaign on Serbia ended the war.

Kosovo is already recognized by 117 countries, including the U.S. and most of the European Union member states. Spain, Romania, Greece, Greek Cyprus and Slovakia are EU nations that have not recognized Kosovo, a landlocked country with a predominantly Albanian population of 1.9 million, as an independent state.

In November 2015, Kosovo failed to become a member of the U.N. cultural organization UNESCO after Belgrade lobbied against the application. But Kosovo joined the European football body UEFA and the international soccer body FIFA in May 2016.