Along Highway 80, the main road heading into Iraq, sand berms, concertina wire and guard posts surrounding military bivouacs stretch across the bleak Kuwaiti desert almost as far as the eye can see. What once were scattered outposts have multiplied and expanded so much that they have nearly converged into a single tent city, a still-building force representing U.S. military might poised to attack.

As diplomacy heads into its final chapter at the United Nations, U.S. officers here say the Bush administration has amassed enough forces around Iraq to march on President Saddam Hussein whenever the order comes. While the focus at U.N. headquarters in New York is on disarmament and Iraqi cooperation with weapons inspectors, the focus in the Persian Gulf region is on fine-tuning the growing U.S. military machine and getting ready for a war that appears increasingly imminent.

"We're ready," said Maj. Gen. Buford C. Blount III, commander of the Army's 3rd Infantry Division, one of the major units here in Kuwait. "We've got everything we need. We're just waiting on the word, the decision from the president on whether we're going to do anything."

From F-15 pilots roaring off runways in Qatar to sailors preparing Tomahawk missiles aboard ships in the Persian Gulf and eastern Mediterranean, from the crews of advanced B-2 bombers on Diego Garcia in the Indian Ocean to M1 Abrams tank drivers practicing here in the Kuwaiti desert, more than 200,000 U.S. troops and another 25,000 Britons have deployed within striking distance of Iraq.

U.S. planes assigned to the campaign fly out of 30 bases in a half-dozen countries. Five aircraft carrier battle groups have been dispatched to the region. And another is on the way. The 101st Airborne Division with its shrink-wrapped helicopters plans to arrive in Kuwait by the middle of this week, while the 4th Infantry Division and other U.S. forces await final word from the Turkish parliament before deploying along Iraq's northern frontier. The impact of a vote in Turkey on Saturday rejecting the U.S. request to use the country was unclear.

Even once it reaches its peak in the next week or two, the force here will represent less than half of the three-quarters of a million U.S. and allied troops who gathered for Operation Desert Storm in 1991 to expel Iraqi troops occupying Kuwait. U.S. commanders believe that with the advancement of technology and the experience of 1991, they will be able to focus more firepower more accurately and lethally than ever before.

"There are sufficient forces in place to do whatever the president asks them to do and they're certainly trained and ready," said Army Col. Rick Thomas, chief spokesman for the U.S. ground forces in Kuwait.

A month ago, the bustling town dubbed Camp Ripper did not exist here in northern Kuwait. Now it has hot showers, Internet hookups, plywood-floored tents with electricity, hot meal service twice a day and a camp PX with two-hour lines for cigarettes and junk food -- and 8,000 heavily armed residents.

"When we got here, there wasn't nothing but nothing," said Cpl. Byron Woods, 31, who served in the infantry during the Persian Gulf War and has returned as a Marine communications specialist.

"The last time we were here," recalled Gunnery Sgt. Nick Hentges, another Gulf War veteran, "the infantry was living in holes. We didn't have any of this."

Hentges, logistics chief for the 3rd Battalion, 7th Regiment of the 1st Marine Division, is essentially responsible for getting 1,000 Marines into Iraq with everything they need to fight. "Beans, bullets and Band-Aids," he summarized.

The other day he surveyed the desert parking lot of trucks, a field of antennas planted as if they were a crop. His wife had to mail him two 42-cup coffee makers from California. When hats were in short supply, she bought 10 in each size and sent them to Kuwait as well.

By now, more than 110,000 U.S. troops and 18,000 British troops have arrived in Kuwait, jostling for room in a nation of only 6,880 square miles. The Kuwaiti government has cordoned off the northern half of the country as a military reservation, but even that does not seem enough.

In the south, outside that zone, Camp Arifjan, the main supply base, has seen its population surge to 12,000 in recent days; a highway that was not there two weeks ago now leads into the secure fortress.

The U.S. ground forces in Kuwait divide about evenly between Army and Marines, but all will fight under a single commander, Army Lt. Gen. David D. McKiernan.

The Marines, who expect to be among the "breaching forces" that launch into Iraqi defenses, have about 55,000 men and women here with another 8,000 due in the days ahead, organized under the 1st Marine Expeditionary Force. Unlike in 1991, when a sizeable force of Marines remained on ships in the Persian Gulf in a bluff to make Iraqis fear an amphibious assault, most Marines have come ashore, including the Amphibious Task Force East from Camp Lejeune, N.C., and Amphibious Task Force West from Camp Pendleton, Calif. At the moment, just the 24th Marine Expeditionary Unit, also from Camp Lejeune, with 2,300 Marines, remains afloat in the eastern Mediterranean.

Camped alongside the Marines in Kuwait is the Army's 3rd Infantry Division, a mechanized unit with about 21,000 soldiers and hundreds of tanks and armored vehicles. Under a different name, it executed the famous left-hook advance into southern Iraq during Desert Storm. Like other Army units arriving in the region, it will be commanded by the 5th Corps headquarters from Germany, which itself has dozens of aviation and combat support units here.

'A War of Bridges'

"Lay ho! Heave!"

"Shake it, shake it, shake it!"

"Toward the gap!"

Two dozen sweaty, panting Marine engineers lifted, shoved and forced massive aluminum girders into place, piece by piece. Anchored by a heavy support structure, a long, thin section stretched across a 50-yard ravine until it hit ground on the other side, then the skeleton of a bridge was rolled across. From pallets of parts to full-fledged bridge, it took Alpha Platoon one hour and 59 minutes, giving them victory in a training contest in the Kuwaiti desert.

"This is what we call brute-force engineering," said Lt. Col. Rick Nelson, commander of the 8th Engineer Support Battalion. "It's all about muscle, lift, coordination."

It is also about winning a war. Long a staple of the U.S. military, combat engineers could prove a critical part of any stab into Iraq, through which the Tigris and Euphrates rivers flow. If Hussein blows up dams as U.S. intelligence predicts he might, it will fall to units such as Nelson's to keep the invasion force moving toward Baghdad. A bridge put up in two hours can hold a 70-ton tank.

"This is going to be a war of bridges," predicted Lt. Thomas Tragesser, 32, who led the winning platoon.

Among the tens of thousands of troops here are specialized units gearing up for challenges that might face them in the Iraqi desert. Hundreds of bulldozers have been shipped in to knock down sand berms. Chemical and biological specialists have set up detection equipment throughout the region. Military police are bracing for mass surrenders.

Many forces en route also bring with them specialties that give a clue about how the military expects to wage the war. The 101st Airborne Division, with 20,000 soldiers and more than 200 helicopter gunships and transport helicopters, could play a lead role in any assault by virtue of its speed and ability to strike from the air.

Other forces trained in parachute jumps could be used to capture Iraqi air bases or seize oil fields. The 82nd Airborne Division's 2nd Brigade is in Kuwait and the 173rd Airborne Brigade, based in Vincenza, Italy, has received a deployment order.

The Army is also dispatching 10,000 soldiers from the 3rd Armored Cavalry Regiment, a lethal, fast-moving unit equipped with M1 Abrams tanks, M2A3 Bradley Fighting Vehicles and AH-64 Apache helicopters. While it remains unclear where the unit is heading, the regiment belongs to the Army's 3rd Corps, just as the 4th Infantry Division does, leading some analysts to conclude it will be part of an invasion force out of Turkey.

After successes in Afghanistan, military commanders plan to rely heavily on special operations units such as the Army Special Forces and Navy SEALs to take out key targets and search for nuclear, chemical or biological weapons. Even the Marines are establishing their largest force reconnaissance unit ever to take on some of those specialized missions, said Capt. David T. Romley, a Marine spokesman.

"This campaign is going to be fought a different way," said retired Army Col. Robert Killebrew. "Desert Storm was fought a lot on the Warsaw Pact model of war while this war will be fought on a new model, and that new model uses special forces a lot more."

Eye on the Battlefield

On a still-peaceful night at a secret base in the Persian Gulf region, Lt. Col. Gary Fabricius prepared for another mission, a complicated task considering the modest size of the aircraft he was about to launch. Fabricius is the squadron commander in charge of sending aloft the Air Force's favorite new weapon over southern Iraq, the unmanned Predator spy plane.

The $3.2 million high-tech drone looks like a baby plane, barely twice a person's height in length and light enough that it can be pushed around the tarmac by two maintenance workers. For nearly 20 hours a day, the Predators buzz over enemy territory beaming back intelligence. Armed with Hellfire missiles, they can also attack, as a CIA-operated drone did last fall when it destroyed a vehicle carrying six suspected al Qaeda activists in Yemen.

But the Predator might be used in a war against Iraq for its most critical role, giving real-time pictures of an unfolding battlefield. "The leadership loves the real-time video," said Fabricius. "We're the eyes over the battle space for the commanders."

He and his team of pilots, sensor operators and communications specialists are studying possible targets in Iraq. "Our major role is to sanitize the battlefield," said Service Airman Medric Jones. "We will need to make sure our own guys aren't walking into danger."

The Predator is part of an aerial armada in the region, including AWACS airborne command aircraft, EC-130 electronic combat aircraft, F-16C/J fighters with HARM missiles and F-15C fighter jets. Altogether, the United States has 700 Air Force and Navy airplanes in the region and 200 Marine planes, with another 150 from the Air Force on the way. The air campaign will be commanded from a computer center at Prince Sultan air base in Saudi Arabia overseeing aircraft flying out of 30 bases in Turkey, Kuwait, Qatar, Oman, the United Arab Emirates and Diego Garcia.

B-2 stealth bombers and F-117 stealth fighters would fly the leading edge of an air attack. While the F-117s were among the first to attack Baghdad during the Gulf War, the B-2 bombers were not deployed in combat until Kosovo in 1999.

The B-2s will operate out of Diego Garcia, possibly Britain and maybe even their home base in Missouri, refueling en route. The F-117s will fly out of Qatar, according to the Air Force. The Air Force, with 27,000 troops in the region, has also deployed B-1B bombers, which can carry even bigger payloads, and will send elements of two B-52 bomber wings.

Complementing the Air Force attack would be the Navy's 5th and 6th Fleets, which now have 70,000 personnel in the region as well as five aircraft carriers and 40 other warships and submarines. The USS Harry S. Truman, the newest carrier in the fleet, and the USS Theodore Roosevelt are in the eastern Mediterranean, while the USS Constellation, USS Abraham Lincoln and USS Kitty Hawk are in the Persian Gulf.

The USS Nimitz will sail Monday from San Diego, officially to replace the Lincoln in April, although commanders could keep six carriers here for a while. Each carrier has about 50 strike aircraft; the Lincoln hosts the first dozen F/A-18E Super Hornets, with a longer range and bigger payload.

"Four, five, six carriers give you the ability to sustain the campaign 24 hours a day," said a retired Navy officer who asked not to be named. "I would anticipate everything would be flying."

Loeb reported from Washington. Correspondent Peter Baker in Kuwait contributed to this report.

Top, 1st Marine Expeditionary Force troops walk about a sprawling tent city in Kuwait called Living Support Area 7, close to Iraq's border. Above, Marines with the 1st Battalion, 4th Marine Regiment arrive at Living Support Area 1.