US Vice-President Dick Cheney visited Afghanistan on Thursday and met President Hamid Karzai ahead of a NATO summit where Washington will urge its allies to send more troops to the war-torn country.
Nato's Afghan mission is one of the toughest challenges faced by the 59-year-old alliance and has led to open differences among allies over strategy and troop levels.
Mr Cheney said the mission of the Nato-led International Security Assistance Force (ISAF) in Afghanistan would be high on the agenda of the summit in Bucharest in early April.
"ISAF has made a tremendous difference in the country and America will ask our NATO allies for an even stronger commitment for the future," Mr Cheney told a news conference in the Afghan capital, Kabul, where he made an unannounced visit.
ISAF has some 43,000 troops in Afghanistan fighting Taliban militants, who have regrouped since US-led and Afghan forces toppled the hardline Islamist movement from power after the September 11th, 2001 attacks and relaunched their insurgency two years ago.
US, British, Canadian and Dutch troops are engaged in the bulk of the fighting in southern and eastern Afghanistan, while other NATO allies, notably France and Germany, have so far resisted US pressure to allow their soldiers to operate outside the relative safety of the north of the country.
"The United States and the other members of the coalition need to have a sufficient force here to be able to ensure security to deal with the threat that's been represented by continuing activities by radicals and extremists, the likes of the Taliban and al Qaeda," Mr Cheney said.
The vice president later travelled to Bagram base near Kabul where a suicide bomber killed 14 people, including a US and a South Korean soldier, the last time he was there in February 2007.