Canadians should brace for casualties as troops head to confront Afghanistan insurgents in the heart of Taliban and al Qaeda territory, a defence expert says.

While he said Afghanistan is relatively safer than Iraq for military personnel, Canadians should not discount the fact that some of their soldiers will not be coming home.

"I think any country, such as our good friends and neighbours the Canadians, sending (more than) 1,500 troops to Afghanistan has to expect a number of casualties in the coming months," said Brookings Institution scholar Michael O'Hanlon, appearing on CTV's Question Period.

"Unfortunately I think the reality is one has to brace for a number of casualties," he said.

One senior Canadian officer conceded that the military was expecting casualties, but would not say what the estimate was.

"We are prepared for casualties but in terms of detailed numbers, no...we are not prepared to release them," said Colonel Steven Noonan, the commander of Task Force Afghanistan, on Question Period.

The Canadian missions to Afghanistan will involve about 2,000 troops over 12 months.

The focus of Canada's operations will move from the capital city of Kabul to the more volatile southern region of Kandahar.

Noonan shed some light on the main violent tactics used by insurgents in the nation.

"Right now the weapons of choice of the terrorist groups operating in Afghanistan are suicide bombers and improvised explosive devices activated by personnel remotely," he said.

For the most part, Taliban and al Qaeda militants are believed to be located in rural regions, not major cities.

"Certainly the Taliban and al Qaeda together are showing a bit of resurgence of late, which makes one worry and wonder if they might be able to extend their presence a bit more into the populated areas in the coming months," O'Hanlon said.

"The estimates are there are still only a few thousand insurgents; but on the other hand, that's enough to cause a lot of havoc and actually to move around quite a bit."

O'Hanlon warned that troops shouldn't rule out the possibility of increased insurgent activity in Kandahar and Kabul in the coming months.

Noonan recently told The Globe and Mail that his soldiers are likely to be at their most vulnerable after the September election, when they transfer operations to Kandahar, down the only highway linking the two cities.

Casualties have been relatively light since Canadians were deployed to Afghanistan in 2002.

The single worst incident was in the same year, when a U.S. warplane attacked Canadian troops on a night-time exercise near Kandahar, killing four.

Despite the dangers the soldiers are likely to encounter in Afghanistan, Noonan said he deemed the operation to be an acceptable risk.

"To be frank, I wouldn't be here if it wasn't an acceptable risk. Of course, we all signed up as soldiers ... and are very aware of the risk," he said.