WASHINGTON - Facing eroding public support for the war in Afghanistan, Defence secretary Robert Gates said Thursday that the Obama administration's effort in the 8-year-old conflict is "only now beginning."

Gates also said he disagrees with people who say it is time to get out of Afghanistan.

Several recent public opinion polls have shown Americans expressing declining support for the idea of sending more troops to the conflict and falling confidence in how the campaign is going. But at a Pentagon news conference, Gates challenged the public perception that the effort is getting away from the administration.

"I don't believe that the war is slipping through the administration's fingers," Gates said. "The nation has been at war for eight years. The fact that Americans would be tired of having their sons and daughters at risk and in battle is not surprising."

Gates argued that President Barack Obama's new strategy in Afghanistan has not been given a chance to work.

"I think what is important to remember is the president's decisions on this strategy were only made at the very end of March; our new commander appeared on the scene in June," Gates said, adding that the extra troops Obama ordered are not even all there yet, nor is the "civilian surge" he wants on hand to help.

"So we are only now beginning to be in a position to have the assets in place and the strategy or the military approach in place to begin to implement the strategy," he said.

The new U.S. and NATO commander, Gen. Stanley McChrystal, delivered a classified assessment Monday of how the war is going and is expected in the coming weeks to ask for more troops and money to turn the war around.

Obama is reading the report during his vacation at the Camp David presidential retreat north of Washington, his aides said.