KABUL, Afghanistan — A landmark constitutional convention began in Afghanistan on Sunday with solemn prayers, the hopeful songs of children and a stirring speech by the nation's former king, who echoed the aspirations of his war-weary countrymen with a call for unity and peace.

With Canadian troops standing watch from a hill, some 500 delegates - from village mullahs to western-educated exiles - gathered under a huge tent at a college in the Afghan capital to hammer out a new constitution in a traditional loya jirga, or grand council.

They are expected to spar over the role of Afghan women, Islam's place in politics and the sharing of power in a nation accustomed to fighting over it.

"The people are relying on you and you should not forget them," the 88-year-old former monarch, Mohammad Zaher Shah, told the assembly. "I hope you will try your best to maintain peace, stability and the unity of the Afghan people."

The loya jirga is a key step in the two-year drive to stabilize the country under an empowered central government, and is supposed to lead to landmark national elections slated for June.

The king spoke after a reading from the Qur'an, Islam's holy book and a rendition of Afghan folk songs by a group of young children, wearing Nike shirts under richly embroidered traditional vests, that brought several delegates to tears.

"This constitution will determine the political, social, and economic future of Afghanistan," President Hamid Karzai said. "This constitution will guarantee the rights of all Afghan people ... and put an end to anarchy."

Security was tight on warnings that Taliban militants might try to attack the convention. Afghan soldiers lined the roads leading to the meeting site, and everyone entering the tent - including the delegates - was checked for weapons and explosives.

From the vantage point of the hill, Canadian soldiers monitored the surrounding areas for any suspicious activities. Nearly 2,000 Canadian troops are in Kabul as part of NATO's International Security Assistance Force, or ISAF, approved by the UN Security Council to provide security to the interim Afghan government.

Master Cpl. Kevin Smith said the Canadians have a bird's-eye view of everything that could potentially pose a threat to the conference. Pointing to comrades higher up at the crest of the hill, Smith said: "They get to do the main observation onto the site up there, and we do the lower part to keep an eye on the mountains."

Many of the Afghan delegates wore fine silk robes, some with western suit jackets slung over them. Yellow, burgundy and cream-coloured turbans jutted out from the crowd.

Female representatives arrived in all-enshrouding burkas, but took them off once inside.

For U.S. officials pushing the process, the Afghans' experience could provide lessons for Iraq, where American administrators have faced an even tougher task in drawing up a constitution. American and Iraqi leaders have differed over how to even start drafting the document. A timetable calls for elections to choose delegates for drafting an Iraqi constitution in early 2005 - about two years after Saddam Hussein's fall.

American officials hailed the start of the gathering in Kabul.

"To the members of the loya jirga, I say you are making history," said U.S. Ambassador Zalmay Khalilzad in an open letter. "The people you represent are watching you with great anticipation. And the world is watching as well."

It could take 10 days to several weeks for the loya jirga, meeting at a Kabul college campus, to finalize a 160-article draft drawn up by a constitutional commission.

Delegates are divided by pressure from U.S.-backed Karzai for a strong chief executive, with opponents pushing for a prime minister who would share power. Karzai said this week he would not stand in next year's elections if a strong prime minister's post is created.

Karzai scored an early victory Sunday evening when an Islamic moderate viewed as a close ally was elected chairman of the council. Sibghatullah Mujaddedi, an aristocratic former president, secured 252 votes.

Some fear the power struggle will overshadow issues like the rights of women, or that the president would bargain away too much to religious hardliners in return for their support for a presidential system.

In Sunday's debate, speakers aligned with the northern alliance, the anti-Taliban coalition dominated by ethnic Tajiks from the north, challenged Karzai's right to appoint 50 of the delegates to the loya jirga.

"The order issued by the president is completely illegal," said Hafiz Mansour, a Kabul delegate and publisher of a weekly newspaper close to the alliance.

But Pashtuns - the country's largest ethnic group - rallied around Karzai, saying his appointment by the last loya jirga in June 2002 gave him authority.