Updated

U.S. Secretary of State Condoleezza Rice said Thursday she has seen progress in Afghanistan during the past few years, despite a determined Taliban insurgency that has disrupted security and prompted concerns that the NATO-led military campaign is failing.

"Can we all expect the security situation will still be difficult — yes, because Afghanistan has determined enemies who laid waste to this country over a period of a decade," said Rice, adding that it would be unfair to say the NATO and Afghan government efforts aren't working. "The strategy is one that I believe is having a good effect."

Afghan President Hamid Karzai, standing beside Rice at a news conference, also defended his leadership, saying the economy and education systems have improved under his watch and there are more democratic freedoms under a new constitution.

"Afghanistan, if given more attention, would be very, very glad and thankful but it is not right that Afghanistan has been forgotten," said Karzai, who was responding to a recent independent report that said the country is in danger of becoming a failed state.

Said Rice: "If you look at the Afghanistan of 2001 and the Afghanistan of now, there is a remarkable difference for the better."

In a show of unity, the secretary made the unannounced trip to Kabul and Kandahar — a former Taliban stronghold — with British Foreign Secretary David Miliband so they could get a firsthand look at the front lines of the NATO-led fight as they lead an effort to boost the number of NATO combat forces in the country.

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.

The U.S. contributes one-third of NATO's 42,000-member International Security Assistance Force mission, making it the largest participant, ahead of Britain with about 7,700 soldiers in Afghanistan. The U.S. has another 12,000 to 13,000 troops there involved in counterterrorism operations.

The high-level U.S.-British visit comes in the bloodiest year in Afghanistan since the U.S.-led toppling of the Taliban in 2001. More than 6,500 people — mostly insurgents — died in violence in 2007, according to an Associated Press count of figures provided by local and international officials.

Rice chalked up the deteriorating security in the country to "committed enemies" of Afghanistan and the United States and she told reporters that U.S. President George W. Bush, after the Sept. 11 attacks by Osama bin Laden's al-Qaida terrorists, had warned people that "this would be a long war."

The Taliban and al-Qaida-linked militants have turned to suicide bombings and other tactics that make it more challenging to fight, she said.

"It's not work that's going to be completed overnight," Rice said of the efforts to rebuild the country and fight insurgents at the same time.

Earlier Thursday, Rice said the Afghan government must meet its responsibilities in fighting the Taliban.

"This is a two-way street, and I think everybody has to step back and concern ourselves with the Taliban," she told reporters.

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. Canada has threatened to remove its combat forces 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.

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.