Syria is descending into a Somalia-style failed state run by warlords, which poses a grave threat to the future of the Middle East, former peace envoy Lakhdar Brahimi has said.

Brahimi, who stepped down a week ago after the failure of peace talks he mediated in Geneva, said that without concerted efforts for a political solution to Syria's brutal civil war "there is a serious risk that the entire region will blow up."

"The conflict is not going to stay inside Syria," he told Der Spiegel magazine in an interview published at the weekend.

More than 160,000 people have been killed in the conflict, which grew out of protests against President Bashar Assad in March 2011, inspired by uprisings in the wider Arab world.

Brahimi said many countries misjudged the Syrian crisis, expecting Assad's rule to crumble as some other Arab leaders' had done, a mistake they compounded by supporting "the war effort instead of the peace effort".

The civil war has drawn in powerful regional states, with Sunni Gulf monarchies and Turkey supporting the rebels and foreign jihadists. Shi'ite Iran, Lebanon's Hezbollah and Iraqi Shi'ites back Assad.

Major powers at the United Nations have also been divided, paralyzing diplomatic efforts. Assad's Western foes have pressed for action against Syrian authorities, but Russia and China have vetoed draft resolutions against Syrian authorities.

Brahimi, who resigned as United Nations special envoy for Afghanistan in 1999, drew comparisons between Syria now and Afghanistan under Taliban rule in the lead-up to the Sept. 11, 2001, attacks on the United States.

"The UN Security Council had no interest in Afghanistan, a small country, poor, far away. I said one day it's going to blow up in your faces. It did," he said. "Syria is so much worse."

He also compared it to Somalia, which has suffered more than two decades of conflict. "It will not be divided, as many have predicted. It's going to be a failed state, with warlords all over the place."

Assad's forces have consolidated their grip over central Syria but swathes of its northern and eastern provinces are controlled by hundreds of rebel brigades including the Islamic State in Iraq and the Levant and other powerful Islamist groups.

Opposition 'likely used chemical weapons'

War crimes were committed daily by both sides in Syria, with starvation used as a weapon of war, civilians held as human shields and chemical weapons used in battle, Brahimi said.

Rebels appeared to have been behind at least one incident in Aleppo province in March 2013, he said.

"From the little I know, it does seem that in Khan al-Assal, in the north, the first time chemical weapons were used, there is a likelihood it was used by the opposition."

UN investigators have not made direct accusations about responsibility for several chemical attacks, including a sarin attack which killed hundreds outside Damascus last August.

But a team of human rights experts said three months ago the Khan al-Assal and Damascus perpetrators "likely had access to the chemical weapons stockpile of the Syrian military".

Brahimi's failed peace effort focused on persuading the United States and Russia to bring together the government and opposition in Geneva. In the end, getting them to sit down in the same room yielded nothing.

"Neither Russia nor the U.S. could convince their friends to participate in the negotiations with serious intent," he told the magazine, adding that the two parties came "screaming and kicking", against their will.

The government negotiating team only went to Geneva to please Moscow, he said, believing that they were winning the war militarily. Most of the opposition also preferred to settle the conflict on the battlefield, and arrived completely unprepared.

Brahimi said Saudi Arabia and Iran, the main powers on either side of the region's Sunni-Shi'ite Muslim divide, had "to start discussing not how to help warring parties, but how to help the Syrian people (and) their neighbours."

But despite hints at rapprochement the two powers remain wary of each other. Saudi Arabia also refused to meet Brahimi, making his task of forging a consensus nearly impossible.

"I think they didn't like what I was saying about a peaceful and negotiated settlement with concessions from both sides," Brahimi said.

