BRUSSELS, Belgium — NATO member states have refused to send any reinforcements for the mission in Afghanistan despite appeals from the organization’s leaders for 2,500 extra troops to fight Taliban insurgents.

The delay will be seen as a further sign that most countries are reluctant to commit troops to the south of Afghanistan, where pitched battles between militants and British and Canadian forces have resulted in the deaths of more than 30 British troops.

Prime Minister Blair said yesterday that NATO countries had a “duty” to respond to the call by the alliance’s secretary general, Jaap de Hoop Scheffer, for more forces. Germany, France, Spain, and Turkey have been mentioned as countries that could do more.

Mr. Blair said British forces were fighting “in difficult circumstances and fighting brilliantly.” He said the September 11, 2001, attacks came out of Afghanistan. “The Taliban and Al Qaeda training camps were the reason we went there, and it is of fundamental importance to the security of this country, never mind the world, that we make sure the job is done properly.”

The plight of British troops, who are taking the brunt of Taliban attacks in Helmand province, was underlined by Britain’s Foreign Office minister, Kim Howells, who told the House of Commons foreign affairs committee that he had spoken to the commander of the NATO forces in Afghanistan, Lieutenant General David Richards, and it was clear that backup was needed.

“We need NATO to be pulling its weight. They need to put more resources in there,” Mr. Howells said.

Secretary of State Rice said Afghanistan could “come back to haunt us” if the West once again allowed it to become a failed state. Referring to an American decision to give the country a lower priority after the withdrawal of the Soviet Union in 1989, Ms. Rice said, “We all came to pay for that.”

A NATO spokesman said he saw “positive indications” that some allies might consider providing additional forces but that it might not come until a meeting of NATO defense ministers in two weeks in Slovenia to finalize offers.

NATO’s American military commander, General James Jones, has expressed concern that delays in reinforcements would allow insurgents to slip back to regroup. Although NATO officers maintain that the 13-day old Operation Medusa, led by the Canadians in one section of Kandahar province, is close to achieving its military objectives, Taliban attacks in Kandahar and Helmand have surprised NATO troops and dragged the alliance into its first major land battles since it was founded in 1949 to defend Europe from Soviet attack.

General Jones last week made a very public demand for up to 2,500 new troops, shortly after returning from what officials said was a sobering inspection visit to Afghanistan. Twenty thousand troops are in the NATO-led International Security Assistance Force, and another 15,000 American troops conducting what American government calls “Operation Enduring Freedom.”