The buildup of American land, sea and air forces in the Persian Gulf is accelerating, with two and possibly three more aircraft carriers likely to head for the region in the next few days, officials said.

On Thursday, the Army's 101st Airborne Division received orders to deploy to the Persian Gulf region, an Army statement said. The statement did not say where the division was going or how many of its 20,000 soldiers would be on the move. The division is outfitted with 270 helicopters.

In addition to the three carriers within striking range of Iraq and a fourth on its way, the Navy is prepared to dispatch the USS Kitty Hawk from its station in Japan and the USS Nimitz from San Diego. If still another were needed, to total seven, it likely would be the USS George Washington from Norfolk, Va.

The number of U.S. troops in the region now stands at about 113,000 -- nearly half of them in Kuwait, the main launch point for a U.S.-led ground invasion -- and it is expected to reach 150,000 by Feb. 15, a senior official said Wednesday.

President Bush says he has not made a decision on using force to disarm Iraq. Secretary of State Colin Powell said Wednesday, in arguing the administration's case against Saddam Hussein before the U.N. Security Council, that the time is approaching for the world to declare "enough is enough."

U.S. forces have been assembling in the Gulf region since December, including a seven-ship Navy fleet that entered the Red Sea this week carrying about 7,000 Marines from the 2nd Marine Expeditionary Brigade at Camp Lejeune, N.C. A similar size group of California-based Marines is en route to the Gulf on seven other ships.

There are about 50,000 troops in Kuwait and that number will climb further, officials said.

A senior defense official who is familiar with U.S. military planning for possible war in Iraq said the Navy will have six or seven aircraft carriers within striking distance of Iraq by the end of this month. Three are within range now -- the USS Harry S. Truman in the Mediterranean Sea and the USS Abraham Lincoln and the USS Constellation in the Persian Gulf or Arabian Sea -- and a fourth, the USS Theodore Roosevelt is en route.

If the Kitty Hawk went to the Gulf, the USS Carl Vinson would replace it in the Pacific to maintain a carrier presence within striking distance of North Korea, several defense officials said. During the war in Afghanistan the Kitty Hawk operated in the Arabian Sea with a contingent of special operations forces aboard. This time it would be expected to play the more conventional role of launching air missions over Iraq.

Mid-February is widely thought to be the earliest date that U.S. forces would be ready to launch an invasion of Iraq, but officials -- all of them speaking on condition of anonymity -- said Wednesday that they may need some weeks beyond that. By early March, the size of the U.S. force is likely to exceed 200,000 troops.

Also Wednesday, a veteran analyst of the Iraqi military, Anthony Cordesman of the Center for Strategic and International Studies, said in a new report that Iraq is building a two-ring defense of Baghdad, the Iraqi capital. Iraq also is erecting an extensive structure of barrier and other defenses in key cities, he wrote.

"There are also indications that some elements of the Republican Guards may be training in urban warfare to fight in civilian dress, and that Iraq will deliberately mix such loyalist elements, the security services and popular forces in civilian dress to fight urban battles under conditions where the U.S. and British may find it impossible to distinguish combatants from civilians," Cordesman wrote.

There is no reliable estimate of Iraq's exact military strength, Cordesman said. He estimates there are 389,000 full-time active duty troops, 2,200 to 2,600 battle tanks, 3,700 other armored vehicles, 2,400 major artillery weapons and 300 combat aircraft. He estimates Iraq has 850 surface-to-air missile launchers and about 3,000 anti-aircraft guns.