BRUSSELS -- The United States and major European powers on Monday led an international rush to support Kosovo's declaration of independence but Serbia also gathered international backing for its opposition.

The United States formally recognized Kosovo as the world's newest state.

Britain, France, Germany and Italy announced at an EU foreign ministers meeting that they would soon give Kosovo official recognition.

"The United States has today formally recognized Kosovo as a sovereign and independent state. We congratulate the people of Kosovo on this historic occasion," US Secretary of State Condoleezza Rice said in a statement, adding that diplomatic ties would ensue.

"As Kosovo today begins its life as an independent state, the United States pledges to continue to be its close friend and partner," she said, reaffirming also "our friendship with Serbia, an ally during two world wars."

Serbia vowed to block the territory that it still claims from joining any world body and launched criminal action against Kosovo's leaders for making Sunday's declaration of independence.

Many countries from China, to Romania, Russia and Spain said they opposed Kosovo's independence but its Prime Minister Hashim Thaci said he was confident there would soon be international approval.

Afghanistan was the first nation to officially recognize Kosovo, in a foreign ministry statement that spoke of the need to respect the "will of the people".

The EU foreign ministers meeting in Brussels exposed divisions over how to respond to Kosovo's split from Serbia, which sparked wild celebrations in Pristina but riots in Belgrade.

The ministers said in a declaration that it would be for individual nations to announce their decisions.

The foreign ministers of Britain, France, Germany and Italy announced their intention to recognize Kosovo.

Danish Foreign Minister Per Stig Moeller said 12 to 15 EU states would formally recognize Kosovo on Thursday or Friday, the Danish news agency Ritzau reported.

"I think there is a very strong head of steam building among a wide range of countries who see this as the last piece of the Yugoslav jigsaw," said British Foreign Secretary David Miliband.

Spain -- which has long struggled with Basque separatists -- led EU countries against an independent Kosovo. Romania's President Traian Basescu described Kosovo's declaration as an "illegal" act, the Mediafax news agency said. Romania has a significant Hungarian minority and close ties to Serbia.

EU nations Cyprus, Slovakia and Bulgaria have also opposed independence.

Serbia's President Boris Tadic traveled to New York to address the UN Security Council and Serbia's parliament met in special session to "annul" the independence declaration.

Violence flared across Serbia after the declaration with angry protestors stoning the Belgrade embassies of the United States and Slovenia, current EU president.

Mobs smashed the windows of two McDonald's restaurants and the US embassy before police used tear gas, rubber bullets and batons to disperse them.

More than 5,000 protesters gathered in central Belgrade on Monday for a new demonstration.

Other protests were to be held in the Kosovo towns of Mitrovica, Gracanica and Strpce. Four grenades were thrown at the UN and the EU missions in Mitrovica during the night. Police said only one exploded and there were no reported injuries.

Serbia's leaders say they will stop Kosovo joining the United Nations and other world bodies and take unspecified diplomatic measures against countries that recognize Kosovo's independence.

Serbian police also filed criminal charges against Kosovo leaders for "organizing the proclamation of a phoney state on Serbian territory," the interior ministry said.

The UN Security Council has not recognized Kosovo's independence and Russia was to make a new attempt Monday to make the council oppose the declaration.

China, like Russia a permanent member of the security council, expressed "grave concern" over Kosovo's declaration, which triggered new tensions between the Chinese and Taiwanese governments.

"The unilateral move taken by Kosovo will lead to a series of consequences. China is deeply worried about its severe and negative impact on peace and stability in the Balkan region," foreign ministry spokesman Liu Jianchao said.

Long-time rival Taiwan warmly welcomed the independence declaration.

"In no way should the independence of one nation be denied by another," said the foreign ministry in Taiwan, which has also struggled to gain international recognition. China claims Taiwan is a renegade province which should be reunited with the mainland.

Russia has said that Kosovo's independence could serve as a precedent for the separatist provinces of Abkhazia and South Ossetia in neighboring Georgia.