The government of Qatar is spending millions of dollars to expand Al Udeid, a remote base in the central Persian Gulf.
If President Bush were to order airstrikes on Iraq, this base, about 20 miles from the capital, Doha, would be a critical hub for US warplanes and their aerial pipeline of bombs and supplies.
In the past months, the US military quietly has moved munitions, equipment and communications gear to the base from Saudi Arabia, the control center for American air operations in the Gulf for more than a decade.
About 3,300 American troops are in Qatar, mostly at Al Udeid, where the signs of an American military buildup are unmistakable:
A tent city has sprouted, with warehouses and miles of security barriers, attesting to the US military's focus on protecting troops against terrorist attack.
Freshly paved runways and aircraft parking ramps stretch deep into the desert.
Newly built hangars for fighter aircraft are hardened to withstand aerial attack. Within view from the main 15,000-foot runway are hardened bunkers, presumably for munitions and supply storage.
"It is likely the most capable base in the Gulf region," says William Arkin, a private military analyst.
Soon after Sept. 11, Qatar granted permission for the US to send warplanes to Al Udeid. They flew attack missions over Afghanistan.
Al Udeid also is host to Air Force Red Horse squadrons, rapid-response teams of civil engineers that can repair and build structures such as runways and roads in remote areas.
US officials will not discuss specifics, saying the Qatari government strictly limits what can be said about the American presence. There has been speculation that Al Udeid is being built up as an alternative to, or replacement for, the Combined Air Operations Center at Prince Sultan Air Base in Saudi Arabia. The Saudis have made clear they do not favor a US invasion of Iraq.
Gen. Tommy Franks, commander of US forces in the Middle East, said this year he had no plans to move the air control center. But he added, "That does not mean that I don't have plans to replicate it." He also said early in the Afghanistan war that he was considering moving his Central Command headquarters from Tampa, Fla., to Qatar, although he eventually chose not to.
Al Udeid is among several US military bases in the Gulf area. Nearly 10,000 Army soldiers are at Camp Doha in Kuwait, and 4,200 troops are in Bahrain, headquarters for the Navy's Fifth Fleet. Several thousand are in Saudi Arabia and a few thousand in Oman.