BRUSSELS — America and the European Union’s biggest powers quickly recognized Kosovo as an independent nation today, widening a split with Russia, China, and some EU members strongly opposed to letting the territory break away from Serbia.

The rift was on view for a second day at the U.N. Security Council, which was holding an emergency session to discuss the declaration of independence issued yesterday by Kosovo’s ethnic Albanian majority.

Ethnic Serbs rallying in northern Kosovo angrily denounced America and urged Russia to help Serbia hold on to the territory that Serbs consider the birthplace of their civilization. Protesters also marched in Serbia’s capital, and that nation recalled its ambassador to America to protest American recognition for an independent Kosovo.

Despite clamoring of Serbs to retake Kosovo, Serbia’s government has ruled out a military response.

But the dispute is likely to worsen already strained relations between the West and Russia, which is a traditional ally of Serbia and seeks to restore its influence in former Soviet bloc states. The Kremlin could become less likely to help in international efforts important to America and its allies, such as pressuring Iran to rein in its nuclear program.

Still, for Washington the declaration of independence by Kosovo vindicated years of dogged effort to help a land achieve its dream of self-determination after years of ethnic conflict and repression by Serbia.

Speaking in Tanzania, President Bush declared: “The Kosovars are now independent” — and Washington formally recognized Kosovo as an independent country soon afterward. Germany, Britain, and France also gave their heavyweight backing, saying they planned to issue formal recognitions.

But Russia, Serbia’s key ally, and emerging global power China remained adamantly opposed to Kosovo’s independence, warning of the danger of inspiring separatist movements around the world, including in their own sprawling territories.

As veto-wielding Security Council members, Russia and China both have the power to block any attempt by Kosovo to gain a seat on the international body.

Serbia vowed to fight to the end against any United Nations recognition.

“The so-called Kosovo state will never be a member of the United Nations. Serbia will use all diplomatic means at its disposal to block Kosovo’s recognition,” Foreign Minister Vuk Jeremic of Serbia said.

The Kremlin was already working diplomatic levers to help Serbia achieve that aim.

Russia’s special envoy to the Balkans, Alexander Botsan-Kharchenko, was quoted by the Interfax news agency as saying Moscow expected U.N. Secretary-General Ban to abide by a Security Council resolution that recognized Kosovo as part of Serbia.

Mr. Ban opened today’s Security Council session by citing the many peaceful celebrations that accompanied Kosovo’s declaration but also noting scattered violence.

He said the United Nations had achieved “peace consolidation and the establishment of functional self-government” in Kosovo, including five successful elections. “Kosovo has made considerable progress through the years,” he said.

President Boris Tadic of Serbia, who attended the U.N. meeting, urged the council to oppose Kosovo’s move. “This act annuls international law, tramples upon justice and enthrones injustice,” he said.

Serbia recalled its ambassador to Washington in protest of American recognition for Kosovo, but said it was not severing diplomatic ties. It also withdrew envoys to France and Turkey and was expected to recall others as more nations formally recognized Kosovo as a new state.

“America and the European Union are stealing Kosovo from us, everyone must realize that,” the head of Serbia’s ultra-nationalist Radical Party, Tomislav Nikolic, said.

After an EU foreign ministers meeting in Brussels, Britain, Germany, and France said they would quickly give recognition to Kosovo, a move that would be followed in the days ahead by most of the bloc’s other 24 member states, officials said.

The EU does not recognize nations, leaving that up to its individual members, and Spain, Greece, Romania, and Cyprus have criticized the effort to make Kosovo independent.

Despite that divide, the EU foreign ministers issued a joint statement citing “the conflict of the 1990s” in Kosovo as a justification for the independence declaration.

America and its NATO allies intervened with an air campaign against Serbia in 1999 to end a brutal crackdown on ethnic Albanian separatists that had killed 10,000 people. The territory had been under United Nations and NATO administration since then, although formally remaining part of Serbia.

Seeking to address the concerns of Russia and others about a free Kosovo, the foreign ministers stressed that Kosovo should be an exception to the international rule that national borders can be changed only if all parties agree.

President Putin of Russia has argued that independence without U.N. approval sets a dangerous precedent for the former Soviet Union, where separatists in Russia’s Chechnya region and two areas of Georgia are agitating for independence.

Russian officials hinted last week that if Kosovo declared independence it might retaliate by recognizing the independence claims of Abkhazia and South Ossetia — two Russian-supported provinces in Georgia. Russia’s parliament repeated the threat today.

Today, Kosovo independence took center stage in China’s diplomatic jousting with Taiwan, which has been self-governing since the Chinese civil war in 1949 but which the Beijing regime considers to still be part of China.

China’s Foreign Ministry criticized Taiwan for welcoming Kosovo’s independence, saying the island’s government did not meet the criteria for recognizing other countries.

“It is known to all that Taiwan, as a part of China, has no right and qualification at all to make the so-called recognition,” a Foreign Ministry spokesman, Liu Jianchao, said in a statement posted on the ministry’s Web site.

China has good ties with Serbia and expressed “deep concern” over Kosovo’s independence declaration.

For Beijing, the announcement conjures up one of its greatest fears: that Taiwan could some day make a similar declaration, something China says it would meet with military force. Chinese leaders also worry about separatist sentiments in the heavily Muslim regions of western China.

Spain, which has battled a violent Basque separatist movement for decades, was the biggest European Union nation to oppose Kosovo independence. Greece, Romania, and Cyprus also are against Kosovo’s new status.

In Bucharest, President Traian Basescu called Kosovo’s declaration “an illegal act” — a position rooted in Romania’s traditional close ties with Serbia.

British Foreign Secretary defended the move by Kosovo’s Albanians, saying the EU was keen to close the book on “two decades of violence and conflict and strife” in the western Balkans.

“There is a very strong head of steam building among a wide range of (EU) countries that do see this as the piece of the Yugoslav jigsaw and don’t see stability in the western Balkans being established without the aspirations of the Kosovar people being respected,” he said.