Updated

Secretary of State Condoleezza Rice said Thursday the Afghan government must meet its responsibilities in fighting a resurgent Taliban as the United States and Britain lead an effort to boost the number of NATO combat forces.

In a show of unity, Rice was making the point as she and British Foreign Secretary David Miliband got a firsthand look at the front lines of the NATO-led fight against insurgents in Kandahar, visiting an alliance airfield in this former Taliban stronghold in southern Afghanistan.

"The Afghan government has responsibilities, too," Rice told reporters ahead of her meeting with President Hamid Karzai. "This is a two-way street, and I think everybody has to step back and concern ourselves with the Taliban."

Said Miliband: "We've got responsibilities that we're determined to live up to and obligations that we're determined to live up to and ditto for the Afghan authorities. That's something we want to follow through and at the heart of both our strategies is the belief this has to be done with the Afghan government and in fact led by the Afghan government, with our support."

The stop in Kandahar was a rare side trip outside the Afghan capital by the top U.S. and British diplomats to meet with international forces facing a resurgent Taliban on what was once the movement's home ground.

Rice said the brief unannounced visit was not an attempt to show up European nations that have refused to send fighting troops to Kandahar and other southern regions.

"It's just the rationale of being able to get outside of Kabul and see one of the areas that's been very active," Rice told reporters before the diplomats' arrival. "I don't think there's any message there to anyone."

Miliband said Kandahar's "iconic status in the history and position of Afghanistan" made it a good choice for a visit outside the capital.

Kandahar was the Taliban's stronghold even after the regime was toppled by a U.S. led assault in 2001. U.S. led forces pushed the Taliban forces out of the city in 2006 and 2007, but the area is still dangerous.

Canada has threatened to remove its combat forced based around Kandahar unless NATO supplies about 2,000 reinforcements.

"It's not an overwhelming number of forces that is being sought here," Rice said. "This is a troop contribution level that NATO can meet and should meet."

She and Miliband never left a NATO airfield during a stay of less than three hours in which they met and thanked about 200 troops from NATO nations and others that are working around Kandahar.

"As the debate heats up about what you are doing here, we will be defending you heart and soul," Miliband told them.

Rice and Miliband began their unannounced visit earlier Thursday in Kabul, carrying a joint message of support and prodding to Afghan officials as the U.S. continued a drive to recruit more NATO troops amid a welter of outside assessments that progress in the six-year war is stalling.

In London on Wednesday, Rice said the fight in Afghanistan won't be won quickly and Defense Secretary Robert Gates scolded NATO countries who haven't committed combat troops "willing to fight and die" to defeat a resurgent Taliban.

"I think that it puts a cloud over the future of the alliance if this is to endure and perhaps even get worse," the Pentagon chief said from Washington.

Gates said he's not optimistic that the influx of 3,000 more Marines into Afghanistan this spring will be enough to put the NATO-led war effort back on track. He said he has sent letters to every alliance defense minister asking them to contribute more troops and equipment, but hasn't received any replies.

As he has before, Gates insisted he would continue to be "a nag on this issue" when he meets NATO defense ministers Thursday and Friday in Europe to discuss Afghanistan, but also said that only the Canadians, British, Australians, Dutch and Danes "are really out there on the line and fighting."

All 26 NATO nations have soldiers in Afghanistan and all agree the mission is their top priority. But the refusal of European allies to send more combat troops is forcing an already stretched U.S. military — focused on the Iraq war — to fill the gap, and it is straining the Western alliance.

"I do think the alliance is facing a real test here," Rice said, speaking at a news conference with Miliband in London on Wednesday before they flew together to Afghanistan. "Our populations need to understand this is not a peacekeeping mission," but rather a long-term fight against extremists, she added.

On Wednesday, Britain confirmed that it will not increase the size of its force in Afghanistan. Some NATO nations had hoped Britain would essentially transfer fighting forces from Iraq, where its operations are scaling down.

Britain has about 7,700 soldiers in Afghanistan and will replace infantry troops with more paratroopers during a routine changeover in April. Prime Minister Gordon Brown told lawmakers Wednesday he will continue to push European allies to provide more combat troops.