Afghan President Hamid Karzai warned Wednesday that there would be no hope for peace in his war-ravaged nation without help from its neighbours to combat "terror groups".

"Terrorist networks are by far the major threat to Afghanistan's security," Karzai said at the opening of a global conference in Istanbul aimed at mapping out his country's future.

"They continue to have sanctuaries outside of our border from where they conduct their merciless campaign of destruction.

"Unless regional cooperation is assured to address the core and root of this issue peace in Afghanistan will remain elusive."

Representatives from 20 countries have joined aid agency members at the Istanbul talks, being held almost 10 years after the Taliban militia were driven out of power in Kabul by a US-led coalition.

But the hardline Islamists remain a deadly force in Afghanistan, continuing to wage attacks against Afghan, US and NATO forces.

Kabul, like Washington, has complained that Islamabad is not doing enough against the Taliban and Al-Qaeda whose militants have found refuge in Pakistani tribal areas on the Afghan border.

The Istanbul summit is intended to chart the way ahead for Afghanistan, with the US-led NATO mission already locked into military drawdowns that are scheduled to bring all foreign combat troops home by 2014.

Karzai is expected to announce in Istanbul a second wave of security transfers from NATO to Afghan control in areas in up to 17 provinces.

This will mark the second stage of a transition process that began in July and is scheduled to see Afghans take responsibility for national security by the time NATO winds down its combat mission.

"To restore security in Afghanistan genuine solidarity is a must," Turkish President Abdullah Gul said in Istanbul.

"It is our obligation as neighbours to contribute to Afghanistan's peace, stability, security and wealth. It is also a matter of our common interest."

But the Taliban's resilience was again underlined on Saturday when it killed at least 17 people in a car bomb attack on a NATO convoy in Kabul, the deadliest attack yet on international forces in the Afghan capital.

The Istanbul gathering is taking place a day after a trilateral summit hosted by Gul brought together the presidents of Afghanistan and Pakistan in a bid to ease tensions between the two neighbours.

Tuesday's talks saw Afghanistan and Pakistan agree to cooperate with an investigation into the September assassination of former Afghan leader and peace negotiator Burhanuddin Rabbani.

Kabul had accused Islamabad of refusing to cooperate in the probe of the murder, which Afghan authorities say was planned in Pakistan and committed by a Pakistani suicide bomber.

Pakistan was the Taliban's chief diplomatic backer when it was in power and is regularly accused by both Kabul and Washington of attempting to destabilise its northern neighbour.

Despite the billions of dollars poured into the country since coalition forces ousted the Taliban from power in November 2001, Afghanistan remains one of the poorest countries in the world. Half of its 30 million population lives below poverty line, according to the United Nations.

Absent from Wednesday's conference is US Secretary of State Hillary Clinton who cancelled after her 92-year-old mother died. Her deputy William Burns is taking her place.

Clinton has said Washington is now pursuing a three-pronged strategy of "fight, talk, build", but with the Taliban mounting a series of high-profile attacks, there has been little public evidence of their willingness to talk.

The United States provides more than two-thirds of a total of 140,000 foreign troops currently in Afghanistan.

As well as the US, the other four permanent members of the UN Security Council -- Britain, China, France and Russia -- are taking part, along with US arch-rival Iran which shares a long border with western Afghanistan.

"Ten years have passed since NATO forces went to Afghanistan under the pretext of fighting terrorism," Iranian Foreign Minister Ali Akbar Salehi said in a statement carried by official news agency IRNA.

"Today we witness that the situation there has not improved. There has been no decrease in terrorist activities there and the killing of innocent people continues.

"Therefore, the neighbouring countries of Afghanistan -- Iran, Pakistan and some other countries -- attempted to establish security and stability there."