The first wave of Canadian soldiers left for Afghanistan Tuesday on a mission Canada's top soldier has described as dangerous but necessary.

The 40 soldiers from the Edmonton Garrison are the first of a 250-member provincial construction team or PRT, made up of soldiers, Mounties, members of the Canadian International Development Agency and Foreign Affairs personnel.

"What I told them was first of all how proud I am of them, how confident I am that they are ready to go and do this job,'' Canada's Chief of the Defence Staff, Gen. Rick Hillier, said at Edmonton International Airport.

Over the next few months, the Canada's presence in Afghanistan will grow further as 2,000 Canadian soldiers will be part of the mission to help the Afghan government assert its authority in the region.

Some of the troops could be sent to the southern mountains, and regions still populated by remnants of the Taliban regime and al Qaeda militants.

Last week Hillier called the militants "murderers and scumbags," who "detest" the freedoms and liberties enjoyed by citizens of democracies.

He said Canada is already a terrorist target by virtue of its status as a democratic member of the Western alliance. He said Canada can't let fear of reprisal stop it from confronting the threat.

"The London attack actually tells us once more: We can't let up," he said, referring to the July 7 terrorist bombings in London that claimed 56 lives.

Sgt. Major Shawn Croucher said this mission will carry more urgency than past ones which have involved Canadian troops.

"Most of our missions before have been with the United Nations, trying to keep two warring factions apart, whereas this one, the insurgents are directly targetting military," Croucher told CFRN News at the Edmonton Garrison.

Apart from rooting out terrorists, Canadian soldiers will be charged with training local police and soldiers, patrolling city streets, as well as ensuring that international supplies get through.

This departure marks the first time Canadians have returned to Kandahar since 2002, when four Edmonton-based soldiers were killed in a friendly fire incident. This mission will last 18 months.

CFRN's Sheldon Larmand says the military isn't giving specifics about when the next wave of troops will leave.

"But they are saying that there will be two more flights after today and they will take place sometime before the end of the month."

Canada's elite Joint Task Force 2 commandos are also expected to provide protection for the team, although Department of Defence officials are refusing to provide details or even confirm their participation.

Critics of the PRT mission warn that Canadian soldiers could face dangers in Kandahar similar to those seen by American forces in Iraq.

U.S. officials predict the fighting in Afghanistan will intensify in the coming months as al Qaeda and Taliban fighters attempt to destabilize national assembly elections scheduled for September.