Afghanistan risks falling into civil and regional war if all US and international troops leave as planned by the end of 2014, the conflict-wracked state's former interior minister warned on Thursday.

Mohammad Haneef Atmar, speaking in Washington, also said Kabul's efforts to bring the Taliban to the negotiating table, which the United States sees as crucial to a peace settlement, had failed to attract hard-core insurgents.

Atmar, who served as interior minister between 2008 and 2010, said it was wrong to assume that violence would taper off after a scheduled 2014 pullout of NATO forces, and that 20,000-30,000 foreign soldiers should remain.

"With 450,000, we have a problem at the moment," he told an audience at the Center for Strategic and International Studies think tank, referring to the combined numbers of Afghan security forces and international troops.

"We are making progress in Helmand and Kandahar but we are not making progress in the east and southeast. Why do we believe that after more years Afghans alone will be able to manage that problem?" he said.

The United States has increasingly been looking for a negotiated end to the Afghan conflict given that the insurgency remains virulent more than 10 years after the September 11 attacks prompted American forces to invade the country.

A US troop surge was credited for improving security in the troubled south but Pentagon officials have said President Barack Obama's administration is contemplating scaling back Afghan combat operations much earlier than planned.

Atmar said Afghanistan would only succeed if security gains in hotspots such as Kandahar are built upon and forecast that the Kabul government could fall.

"Why would it fall? If there is a premature drawdown of troops, if there is a significant reduction of economic assistance... and if the vacuum created is to be filled by regional actors," he said, alluding to Afghanistan's neighbors Pakistan, Iran, Russia and India.

"If these things happen we will fall. There will be a perfect scenario for a regional wargame and it will be a proxy-led civil war in Afghanistan which would lead to the disintegration of Afghanistan," he said, noting that such conditions would provide more safe havens for anti-American insurgents.

Atmar, who was also education minister between 2006 and 2008, said the resulting security vacuum would lead the Afghan national army and police to become "factionalized" and loyalty would shift from the state to warlords.

"A significant part of Afghanistan would be controlled by the insurgents and that would provide safe haven to Al-Qaeda, Lashkar-e-Taiba and to all the other groups that do not have problems with Afghans alone," he added.

Lashkar-e-Taiba is the Pakistan-based insurgent group fighting against Indian control in Kashmir and has been blamed by India for deadly violence, most notably the November 2008 attacks in Mumbai that killed 166 people.

US Secretary of State Hillary Clinton last month urged Pakistan to take action within "days and weeks" on dismantling Afghan militant havens and encouraging the Taliban into peace talks, which Atmar said had so far failed.

"Of around 30,000 insurgents, only eight percent have reconciled so far -- and 99 percent of them are not from the south," he said.

"Frankly speaking, it does not work."

Peace initiatives have stalled since ex-Afghanistan president Burhanuddin Rabbani, who had been given the Herculean task of negotiating with insurgents, was killed by a suicide bomber on September 20.

Michael O'Hanlon, an expert on Afghanistan and Pakistan at the Brookings think tank in Washington, described Atmar as "one of the three or four best (people) that Afghanistan has to offer."

"I take everything he says very seriously," O'Hanlon told AFP. "That said, I don't believe our force would have to be quite as large," as 20,000 to 30,000 troops. "But it would have to be more than 10,000 for a while," he said.

Afghanistan and the United States are currently negotiating a strategic partnership that will govern bilateral relations after NATO combat forces -- there are currently 140,000 in the war-torn state -- withdraw in 2014.