U.S. Defence Secretary Robert Gates on Thursday said his criticism of the NATO-led mission in Afghanistan wasn't aimed at specific countries, but maintained the alliance as a whole isn't sufficiently trained in counter-insurgency operations.

Gates held a news conference a day after his interview with the Los Angeles Times caused an uproar among NATO countries fighting in Afghanistan. Pentagon officials said they held the news conference earlier in the day to meet European news deadlines.

Gates is quoted as saying NATO forces in southern Afghanistan do not know how to properly combat a guerrilla insurgency, and that could be contributing to rising violence in the country.

Speaking Thursday at the Pentagon, he said his criticism was aimed at the entire alliance, including the United States.

"I've … said publicly the U.S. military and U.S. government as a whole has had a difficult time adapting to protracted counter-insurgency campaigns in Afghanistan and Iraq.

"We have to acknowledge the reality that the alliance as a whole has not trained for counter-insurgency operations even though individual countries have considerable expertise at and success in this arena. "

When asked if he made any phone calls to soothe potential ruffled feathers, Gates said he had "reached out to" Canadian Defence Minister Peter MacKay.

"They had suffered a loss the day before and I wanted to make sure they understood we have respect for their contribution and how much of an effect they are having," he said.

Gates said he has heard from troops in Afghanistan — not just Americans, he noted — that some soldiers being sent to the country "are not fully trained."

He encouraged countries working in Afghanistan to take advantage of a U.S. "counter-insurgency training academy" in Kabul.

Gates added that an extra 3,300 U.S. marines being sent to Afghanistan doesn't "reflect dissatisfaction" with NATO countries' performance.

Harper says U.S. has always appreciated Canada

In Saskatchewan on Thursday, Prime Minister Stephen Harper insisted that Americans have always supported Canada's military work.

"Officials from the United States at all levels have always conveyed their appreciation and confidence in Canadian forces, and I've heard that from both military and non-military sources," he told reporters in Prince Albert.

"I believe Secretary Gates conveyed that to Minister MacKay yesterday, and so there should be no misinterpretation of those comments vis-a-vis Canada."

The Liberals did not take such an understanding view of Gates's comments. Liberal defence critic Denis Coderre compared it to the time U.S. President George W. Bush failed to thank Canada for its support in a speech given nine days after the Sept. 11 attacks.

"I'm insulted almost as badly as when George Bush ignored Canada … after 9/11, and I think most people feel that way too," Coderre said Thursday.

Could be tipping point, Layton says

NDP Leader Jack Layton, who is opposed to the Afghan mission, said Gates's comments could be the tipping point that drives Canada out of the war.

He predicted Canadians, who are already wary of Canada's role in Afghanistan, will be angered by Gates's words, and that might be enough to sway Parliament against any proposals to extend the mission beyond 2009.

"I think Canadians, just as they rose up and spoke around the war in Iraq —ultimately provoking [Former prime minister Jean] Chrétien to do the right thing at the last moment on the eve of the invasion — the Canadian people need to speak out now," Layton said.

Meanwhile, NATO spokesman James Appathurai said Gates's comments weren't helpful.

"I'll be very frank. I don't think the effect of the L.A. Times piece has been very positive," said Appathurai, speaking to CBC News earlier Thursday.

"It's not helpful when there's media speculation about divisions between allies. It's even worse when there is division between allies, but I don't think there is."

'Impetus to do better'

Appathurai said countries can't be oversensitive when it comes to such criticism.

"We should be very careful not to take concerns about strategy and concerns about training personally, or as personal attacks, or as direct attacks," he said.

Any criticism from Gates should be looked at dispassionately, he said.

"We must be careful not to use this for political gain, not to take it too personally, and use it as impetus to do better," said Appathurai.

Overall, about 27,000 U.S. troops are in Afghanistan, including 14,000 with the NATO-led coalition. The other 13,000 U.S. troops are training Afghan forces and searching for al-Qaeda.

About 2,500 Canadian soldiers are in the southern Kandahar region. Seventy-seven soldiers and one diplomat have been killed since the mission started in 2002.

With files from the Associated Press and Canadian Press