KABUL, Afghanistan (AP) — Afghanistan's chief peace negotiator said Saturday the often fractured Afghan political leadership must unify in its peace talks with the Taliban or risk the withdrawal of U.S. and NATO troops bringing more bitter fighting.

Abdullah Abdullah, head of Afghanistan’s National Reconciliation Council, said the time is now for Afghanistan’s political leaders to stand united in the talks. But some of them are former warlords with fierce reputations, heavily armed militias and deep seated grudges.

In an interview with The Associated Press in the Afghan capital, Abdullah warned that history and millions of Afghans — already frustrated by what they see as government ineptitude and runaway corruption — will judge them harshly if unity eludes the powerful leaders now in Kabul. In the early 1990s bitter fighting between many of the same leaders killed thousands of mostly civilians in the capital and gave rise to the Taliban, who took power in 1996.

Abdullah said the withdrawal that officially began Saturday of the remaining 2,500 to 3,500 U.S. troops and about 7,000 NATO allied forces will present “huge challenges."

“I wouldn’t call it the end of of the world for our people. I would say that it will be very challenging and that’s why I am of the opinion that the whole focus has to be on achieving peace, that does not only take us, it takes the other side," he said.

Still, Abdullah said he is unconvinced the Taliban want peace. He said the National Reconciliation Council, of which he is the chairman, has put out countless calls for the Taliban to put all their demands on the table.

Messages go back and forth between a variety of Taliban to senior negotiators, including himself, said Abdullah. He noted that he has received countless messages from Taliban officials, some written, some as voice messages. Sometimes they are detailed, and other times terse and brief. But he said he has yet to see a commitment to peace from the insurgent group on which he can rely.

Abdullah said his response to the Taliban has been consistent: “Put everything that you want on the negotiating table. We are ready to discuss it. We are ready to find ways that it works for both sides."

He said the withdrawal adds pressure on both sides to find a peace deal.

The Taliban cannot win militarily, he said, and even regional powers — including Pakistan with its influence over the insurgent group — have steadfastly rejected a military takeover in Afghanistan. Taliban leaders are headquartered in Pakistani cities.

An “inclusive, peaceful settlement, this is what everybody believes in. ... God forbid if we don’t have peace then, of course, nobody has forgotten the recent history of the country. So everything has to be done in order to mitigate the serious consequences of the withdrawal.”

Meanwhile, Abdullah questioned assurances Washington has received from the Taliban to reject terrorist groups, particularly al-Qaida, the reason Washington and NATO invaded 20 years ago. Links between the Taliban and al-Qaida have continued to surface and al-Qaida publications and websites pledge allegiance to the Taliban leadership.

“What has happened to al-Qaida?" he asked. "That’s a big question.”