LONDON - Afghanistan could degenerate into a "failed state" if NATO were to pull out troops and abandon efforts to stabilise the country, Foreign Secretary David Miliband said on Monday.

Miliband, who visited Afghanistan last week with U.S. Secretary of State Condoleezza Rice, said "immense challenges" remained there and it was vital that Britain meet its commitments and some other NATO members increased theirs.

"It would help precipitate even more dangerous insecurity in Afghanistan (if the international community pulled out)," Miliband told BBC radio. If more effort is not made, Afghanistan risks becoming a "failed state", he added.

"I think it's important that the pressure is kept up," he said. "But I also think it's important that we emphasise to people that troops alone are not going to be the answer, it has to be the building up of a decent society in Afghanistan that is able to cater for its own affairs."

American-led forces toppled the Taliban government in 2001, but Taliban rebels launched an insurgency two years ago whose success has led Washington to call on its allies to send more troops to Afghanistan.

France has indicated a willingness to send more troops, but Germany has been adamant it cannot do more.

Britain, the second largest contributor to the 43,000-strong ISAF international peace force, is feeling intense pressure as its 7,000 soldiers - based mostly in southern Helmand province - battle increasingly fierce resistance and casualties rise.

"We do need the whole of the international community, including European countries, to step up," Miliband said. "There are a range of ways in which the international community needs to make its presence felt."