WASHINGTON - Joint Chiefs of Staff Chairman Gen. Peter Pace said Sunday that the number of U.S. troops in Iraq could increase next year, not decrease, if the insurgency continued.

Pace"s comments on "Fox News Sunday" suggested that the Pentagon"s plan to reduce the scale of American forces in Iraq, announced Friday by Defense Secretary Donald H. Rumsfeld, depended on several variables.

Pace, like Rumsfeld, said the military and the Bush administration had no specific target for how many troops to keep in Iraq now that the general election was over.

Instead, Pace said, military commanders would continue to closely monitor the Pentagon"s "offramps and onramps based on [the forces] we have on the ground" in Iraq. The four-star Marine general said that any decision to withdraw or deploy additional troops in Iraq would depend mostly on whether the insurgency continued to launch deadly attacks against U.S.-led forces and friendly elements of the fledgling Baghdad government.

"So if things go the way we expect them to, as more Iraqi units stand up, we"ll be able to bring our troops down and turn over that territory to the Iraqis," Pace said on the Christmas Day edition of the talk show. "But on the other hand, the enemy has a vote in this, and if they were to cause some kind of problems that required more troops, then we would do exactly what we"ve done in the past, which is give the commanders on the ground what they need. And in that case, you could see troop level go up a little bit to handle that problem."

Pace, the first Marine appointed to the top military job, also said that U.S. troops probably would be redeployed to specific regions within Iraq based on where the insurgency was strongest and where Iraq"s battalions of young, inexperienced troops were struggling the most.

He said that if Americans were looking at a color-coded map of deployments next year, they would "watch the colors change" as Iraqi battalions took over for U.S. forces.

Rumsfeld announced Friday during a trip to Iraq that President Bush had signed off on the withdrawal of an undisclosed number of U.S. combat troops next year. The Defense secretary did not specify how many of the approximately 158,000 troops would be pulled out but suggested that the number of U.S. combat brigades could drop from 17 to 15, a difference of about 7,000 troops. Pentagon officials also said they planned to withdraw 20,000 U.S. soldiers who were stationed in Iraq to protect against violence in the run-up to the Dec. 15 election.

"The size and composition of the U.S. forces of course will fluctuate as commanders continue to shift their focus to emphasize training and supporting the Iraqi security forces," Rumsfeld told U.S. troops at a "town hall" meeting in Fallouja.

The top U.S. commander in Iraq, Gen. George Casey, also said recently that he had no plans for a particular troop deployment level at the end of 2006. But Casey said he would base troop reductions on Iraq"s progress in forming a government and training its troops.

Also Sunday, former U.S. Secretary of State Colin L. Powell said he was "quite sure" that there would be fewer American troops in Iraq in 2006. "We"re well on our way" to building up the kind of military and police force that the Iraqi government needs before it can take over the reins from U.S. troops, Powell said on ABC"s "This Week."

Powell also said he did not think the Pentagon could sustain the current number of troops in Iraq for very long. "You can"t keep sending them back over and over," he said.

Asked to comment on Bush"s decision to use the National Security Agency to eavesdrop on people in the U.S. without court-approved warrants, Powell said he supported the action, citing the widespread fears that Al Qaeda would launch additional attacks after the Sept. 11 terrorist strikes.

But he also said he thought the Bush administration could have avoided a major controversy and looming showdown with Congress by obtaining warrants for such eavesdropping through the Foreign Intelligence Surveillance Court.

Ultimately, Powell said, it would be up to Congress to determine whether Bush had the legal authority to order the top-secret NSA domestic spying program, or if it amounted to an unlawful circumvention of federal laws established to protect the privacy rights of Americans.

"And that"s going to be a great debate," Powell said.