Out of sight on a remote, scalding-hot air base in Saudi Arabia, some 5,000 American troops fly patrols over southern Iraq and defend this oil-rich desert kingdom.
Also unseen, other American forces man the Patriot antimissile batteries that ring the sandy capital, Riyadh, and other major cities. And American trainers, who call themselves "desert military diplomats," continue to build the close US-Saudi alliance that began more than half a century ago.
"Members of the Saudi Arabian military are our trusted friends and vice versa," the US military says in an official statement. A "most generous and caring people," the e-mail reads, Saudis "recognize and support the need for a US military presence here in their country."
Partly out of concern that their mission will be misrepresented, however and that any story will raise the public profile and sensitivities surrounding US forces in lands holy to Islam requests to visit by journalists are now refused.
Although America provides Saudi Arabia's bedrock security in exchange for secure access to Saudi oil, the extreme low profile is deliberate. It underscores a host of long-growing issues that have been magnified since Sept. 11, overshadowing US ties with its most important Arab ally.
Officially, the two friends are all smiles and as close as ever. But unofficially, the act of balancing interests is getting trickier for both Washington and Riyadh.
Saudi officials rule out using any "oil weapon" to influence Washington. But at stake is Saudi support as Washington seeks to expand its declared "war on terrorism" to Iraq.
Sept. 11 "shattered the fabric" of US-Saudi ties, says Khaled Al-Maeena, editor of the Jeddah-based, English language Arab News. "I don't know why [officials on both sides] say it is business as usual. That's humbug. The majority of Saudis love America, but US-Saudi relations are far from cordial."
Tepid support for US missions against Afghanistan, deep and public unhappiness with unwavering US support for Israel, and public opposition to any military action in Iraq, have caused some ranking US officials to reexamine the scale of US forces in Saudi Arabia.
"Saudi Arabia feels they are in the cross hairs," says a US official here. "They want the war on terrorism to succeed, but don't want it to be seen to be anti-Islamic."
Americans and Saudis alike have been scrambling to pick up the pieces since it became clear that 15 of the 19 hijackers were Saudi. Though Washington has yet to give an official breakdown by nationality of prisoners at Guantanamo Bay, Cuba, one US official here confirmed that more than one-third of the first 300 detainees were Saudis.
Saudi-born Osama bin Laden has called repeatedly for US "infidel" forces to be ejected from the land of Islam's holiest shrines. US and Saudi officials say that the question of US forces moving has not come up at high-level talks. The focus of George W. Bush's Texas summit with Crown Prince Abdullah one month ago was in fact Mideast violence, not unresolved questions about Saudi roots of the Sept. 11 hijackers.
"The indifference toward Saudi Arabia [among Americans] before Sept. 11 has been replaced by great suspicion, if not hatred," says Simon Henderson, a London-based expert on Saudi Arabia who runs Saudi Strategies consultancy. "The great American people have not forgotten 9/11, and if they thought the White House in the name of a bit of cozy realpolitik was trying to sweep it under the carpet, they would be annoyed."
On Afghanistan, the official line on both sides is that the US never asked Saudi Arabia for permission to mount combat operations from Saudi bases, and that Saudi has helped in every other way. Saudi sources say the US did request combat help, and was refused.
Even before Sept. 11, the Pentagon was reportedly working on non-Saudi contingency plans.
Riyadh also opposes Washington's policy of "regime change" for Baghdad.
"Their view is that if the Americans get it wrong, you'll end up with an irate Saddam who is a threat, or a pro-Tehran theocracy that is also a threat," says Mr. Henderson. "And why deal with Saddam at all, if the US security guarantee is that the cavalry will come over the horizon anyway when the kingdom is in crisis?"
"Two more different societies never existed," says a Western diplomat. He calls the Americans and closed-society Saudis "intimate strangers ... that can quite easily talk past each other and easily rub each other the wrong way."
In January, White House Chief of Staff Andrew Card told CNN that the Saudis have been "wonderful allies in this war against terrorism" a view shared by many diplomats here but that Riyadh had been "asking a long time" to reduce troop levels. "We are looking to reduce the footprint within Saudi Arabia," he said, "consistent with America's interests and consistent with the interests of Saudi Arabia."
That view coincided with concern of the chairman of the Senate Armed Services Committee, Carl Levin, who said in January: "There's a real problem when we're told that a country that's presumably an ally of ours doesn't want us to be seen by its people."
American forces moved to the remote Prince Sultan air base, after vulnerable city locations including a US Air Force barracks at Al-Khobar were targeted by bombers in 1995 and 1996.
"We are aware of the pressure around the military presence here and work to keep it low key," says a US official here. "But this is the heart of the relationship.... The idea that people feel threatened by 'crusader, infidel' forces has no traction."
"Osama Bin Laden has tried his [hardest] to put a wedge between Saudi Arabia and the US, by the fact that he chose [so many Saudis] of the suicide group," says Saudi Foreign Minister Prince Saud al-Faisal, in an interview. "But you are an American here: Has anyone stopped you in the street?"
Still, he adds: "A family feud is the most intense feud, and having that closeness and affinity makes it feel like a personal issue."
Indeed, distress over US support of Israel caused Crown Prince Abdullah last August to write to Bush: "We are at a crossroads," he said in the message. "It is time for the US and Saudi Arabia to look at their separate interests."
"The Saudis are looking to move back" from the "intense" US-Saudi ties since the Gulf War, says Gregory Gause, an expert on Saudi Arabia at the University of Vermont. "It is not a divorce, not a 180-degree turn, but something like what pre-dated 1990: cooperation, but with some distance."