France will punish a general who criticised the US-led war effort in Afghanistan, Defence Minister Herve Morin said Wednesday, amid growing doubts about the NATO war strategy.

General Vincent Desportes, director of France's Joint Forces Defence College, which trains staff officers, last week told the daily Le Monde that the situation in Afghanistan "has never been worse".

Desportes said US President Barack Obama appears unsure of his strategy, that the counterinsurgency plan underway on the ground is not bearing fruit and that American soldiers are unhappy with their leadership.

His comments were an embarrassment for President Nicolas Sarkozy's French government, which has 3,500 soldiers in Afghanistan fighting alongside Afghan forces in a US-led coalition against a fierce insurgency.

"He will be punished," Morin told BFM television, adding that he had asked the French chiefs of staff to take administrative action against Desportes, whom he said had shown a "lack of judgement".

"Until we hear otherwise, soldiers are under the authority of politicians, just like any other public employee," he warned.

Desportes spoke out shortly after Obama triggered a new round of doubts over the Afghan war when he sacked the US commander of the NATO coalition, General Stanley McChrystal, over his own comments in the media.

According to the investigative weekly Canard Enchaine, Desportes' concerns over the coalition's strategy are widely shared among senior French officers, one of whom described the war as "an unmanageable shitstorm".

French civilians are also opposed to the war. Opinion polls showed that 80 percent of voters were against Sarkozy's decision last year to reinforce the French contingent with additional troops.

"It's an American war," Desportes told Le Monde, complaining that NATO pays no heed to European concerns. "When you're a one percent shareholder you don't get to speak out. The allies have no strategic voice."