Washington ? As the U.S. military presses ahead with preparations for possible war against Iraq, it is far from clear that an attack to topple Saddam Hussein would begin this winter as once widely believed.

If Iraq refuses to accept a U.N. resolution restarting weapons inspections, a U.S.-led attack could happen by December or January. But, for now, the U.N. Security Council has failed to agree on a resolution to restart tough inspections.

And if Saddam agrees to cooperate with U.N. weapons inspections, at least initially, that could delay military action beyond winter and spring, which are considered the most suitable times for conducting war in Iraq.

Senior U.S. military officials said Tuesday they are ready to act whenever President Bush decides the time is right.

Gen. Richard Myers, chairman of the Joint Chiefs of Staff, was asked at a Pentagon news conference Tuesday whether he was concerned that Iraq has the luxury of time to prepare its defenses against an American invasion.

“I can tell you we’re postured in a way that that will not be a problem,” Myers replied. He said that in strictly military terms, the passage of time can aid both the attacker and the defender.

“The longer you wait, obviously, an adversary has time to prepare but so do you, to prepare for the consequences,” he said.

The U.S. Navy already has two aircraft carrier battle groups within striking range of Iraq and may have four there by December; the Air Force has more than 200 warplanes based in the Persian Gulf area; the Army has several thousand soldiers in Kuwait, and there are a few thousand Marines aboard ships in the region.

If U.S. military action were pushed to summer or beyond, conditions could be more difficult for the invading forces. The gear soldiers wear as protection against chemical or biological weapons, for example, is much harder to function in during the blistering heat of an Iraqi summer. But the heat would not help the Iraqis, either.

“On balance, people would prefer to fight during the spring, but you can make a lot of adaptations,” said Anthony Cordesman, who has studied and written extensively about Iraq’s decade-long war with Iran and the 1991 Gulf War.

“It just doesn’t matter,” he said, because U.S. forces have such overwhelming advantages over the Iraqis.

Bush said Monday he doubts Saddam will reverse himself and accept a U.N. Security Council resolution requiring him to provide unlimited and unimpeded access to suspected weapons areas. If he does, Bush said, “that in itself” would indicate the administration had reached its goal of changing the regime without resorting to war.