U.S. and Afghan officials acknowledge that Taleban forces are posing serious challenges to security in Afghanistan. But they add that, although Taleban fighters are fueling some of the country's worst violence in recent years, the insurgents are no match for NATO and Afghan troops.

US soldiers in armoured vehicle secure site of suicide car bomb blast, in Kabul, Sept, 8, 2006

As the United States looks to mark the fifth anniversary of the September 11th, 2001, terrorist attacks, one country that has come under renewed scrutiny is Afghanistan.

In 2001, the Taleban regime ruled Afghanistan with an iron grip and backed Osama bin Laden, whose al-Qaida terrorist network masterminded the September 11 attacks.

Shortly afterwards, U.S.-led troops helped overthrow the Taleban, and in the more than four years that followed, Afghanistan made progress toward setting up a new government. The president, Hamid Karzai, and the 351-seat parliament are democratically-elected. The country also has a new constitution.

Dick Cheney after appearing on Meet the Press, Sept. 10, 2006, in Washington

On the NBC television program Meet the Press, Vice President Dick Cheney said toppling the Taleban regime also threw the al-Qaida terrorism network into disarray.

"Afghanistan was governed by the Taleban, one of the worst regimes in modern times, terribly dictatorial, terribly discriminatory towards women," he said. "There were training camps in Afghanistan, training thousands of al-Qaida terrorists. All those training camps today are shut down."

But in recent months, Taleban fighters have reappeared in Afghanistan, in force.

Secretary of State Condoleezza Rice told Fox News Sunday she is not surprised they are fighting back.

"Of course they're going to fight back, even if they're on the ropes, they're going to fight back," she said. "And yes, they came back somewhat more organized and somewhat more capable than people would have expected. But that's why they're being beaten back by the NATO forces that are there."

Coalition troops in Kandahar

At the end of July, U.S.-led coalition troops formally handed over control of international military activities in Afghanistan to NATO.

The top NATO commander, U.S. General James Jones last week visited Kabul and said he did not expect what he called the "level of intensity" of Taleban attacks since the handover.

On Sunday, a suicide bomber killed three people in eastern Paktia province, including the provincial governor. Also on Sunday, NATO said its and Afghan troops killed 94 Taleban fighters in southern Kandahar province overnight.

Afghanistan's ambassador to the United States, Said Jawad, told CNN's Late Edition program the Taleban resurgence is significant, but will not derail the country from the process of recovery.

"They [Taleban] are making a serious comeback," he said. "They are a serious security challenge for us right now, but the political process, the reconstruction process, is way advanced by now."

Meanwhile, a debate continues in the United States over the whereabouts of Osama bin Laden, who is believed to be hiding in the rugged, mountainous region along the Afghan-Pakistani border. A front page article in Sunday's Washington Post newspaper said for U.S. officials, the bin Laden trail is "stone cold". Both Rice and Cheney disputed this article, saying the United States is still serious about finding and capturing bin Laden.