Allegations of torture, abuse and execution within the Afghan prison system will be investigated by the North Atlantic Treaty Organization and the Afghanistan government, the head of NATO said Saturday.

Jaap de Hoop Scheffer, the secretary general of NATO, said during a security meeting in Brussels said NATO countries are in Afghanistan to "defend universal values," and the alleged abuse of prisoners handed over to Afghans is not acceptable.

De Hoop Scheffer was just one of a number of top security officials from NATO countries to voice an opinion on the situation in Afghanistan.

The former U.S. ambassador to the United Nations, Richard Holbrooke, said NATO risks losing the war because of a "tremendous deterioration" in the popularity of the government of President Hamid Karzai -- the U.S. backed democratic leader of the country.

"Afghanistan represents the ultimate test for NATO,'' Holbrooke -- who recently toured Afghanistan -- told the Brussels Forum, an annual transatlantic security conference.

NATO has 36,000 troops in Afghanistan, including roughly 2,500 from Canada. In addition, the U.S. has deployed an additional 11,000 troops to the eastern border region with Pakistan -- an area thought to be an entry point for foreign combatants.

But despite the massive resources dedicated to the country, Taliban guerrillas have continued to increase their activities over the past year, in many cases trickling back into areas that were earlier cleared of militants.

Holbrooke Karzai's government has become unpopular because of corruption stemming from Afghanistan's drug problem.

"I have heard increasingly that the government has lost its momentum,'' he said.

"I can sense a tremendous deterioration in the standing of the government. Afghans are now universally talking about their disappointment with Karzai. Let's be honest with ourselves ... the government must succeed or else the Taliban will gain from it.''

Canada's Foreign Affairs Minister Peter MacKay, also attending the conference, spoke about the fragility of the operation.

"While I don't want to sound alarmist, I think there is going to be a tipping point unless we are able to stabilize (southern Afghanistan, especially), unless we are able to get on with building the economy, rule of law and government institutions," MacKay said.

In total, 54 Canadians soldiers have been killed since the U.S.-led invasion in 2002.

MacKay suggested Canada has carried an unequal share of the burden in Afghanistan -- particularly when it comes to combat operations -- and said Canada has been disappointed by the lack of solidarity with other NATO nations.

MacKay also called on Pakistan to do more to shut off the flow of illegal immigrants into Afghanistan.

Holbrooke, who is pegged by some to be named as the U.S. secretary of state if a Democratic president is elected, said U.S. efforts to train the Afghan police have fallen short of the mark, producing a corrupt, incompetent force.

DynCorp, a Virginia-based provider of security and defence services in Afghanistan and Iraq, among other trouble spots, took much of his scorn.

"The U.S. training program (for the police) under DynCorp is an appalling joke ... a complete shambles,'' he said.

In Canada, the federal government has faced intense questioning this week over its stance on the alleged abuse of detainees in Afghanistan -- amid mixed signals about whether the government was aware that such concerns existed about detainee transfers.

With files from the Associated Press