The United States is capable of launching a rapid attack on Iraq by marshaling 50,000 troops at the Kuwaiti border in roughly a week, airlifting them in and bringing their tanks and heavy equipment on ships through the Strait of Hormuz.
That would give Iraqi leader Saddam Hussein just a few days' notice, rather than the six months he had before the 1991 Gulf War. It also might eliminate America's need to rely on bases in neighboring countries like Saudi Arabia or Jordan, whose governments say they want the United States to leave Iraq alone.
A risk is that Saddam still would have time to launch missiles -- perhaps carrying poison gas or anthrax -- toward U.S. troops in Kuwait or civilians in Israel, say military experts eyeing the options if President Bush decides to take on Iraq.
Such a surprise attack also might fall short of the main goal of toppling Saddam, requiring a backup plan involving thousands more American troops.
For now, Bush seems focused on covert action: He signed an order earlier this year directing the CIA to increase support to Iraqi opposition groups and allowing possible use of CIA and Special Forces teams against Saddam.
Bush also recently unveiled a new policy that allows for pre-emptive action against enemies who have weapons of mass destruction.
If covert attempts fail, many expect Bush to try military action, and perhaps look for an element of surprise.
"We could have a situation where on Monday, it first looks like there will be a war, on Friday troops are in Kuwait, and by (the next) Thursday they're in Baghdad," said John Pike, a defense analyst in Washington.
White House spokesman Ari Fleischer said Wednesday that Bush has indicated he's made no decisions on Iraq. "The president is, of course, consulting with nations around the world about all of America's plans, diplomatic and otherwise, in the war against terrorism," Fleischer said.
Many U.S. officials and lawmakers believe 200,000 or more soldiers could be needed to topple Saddam, a force that would require months to move to the region.
The hope behind a swifter attack is that the Iraqi army would crumble in shock if Saddam -- with little warning -- appeared doomed, said retired Rear Adm. Stephen Baker, an analyst at the Center for Defense Information in Washington. Thus, fewer American troops would be needed for success, the argument goes.
U.S. officials might try to delay knowledge of any such impending attack by, at first, explaining the troop movements as merely the beginning of a six-month buildup.
There are risks.
One is that Iraqi troops, especially Saddam's Republican Guard, would not give up, instead bogging American soldiers down in difficult urban warfare within Baghdad.
Using fewer American troops also increases the risk that Iraq might disintegrate into ethnic conflicts if Saddam falls, said Anthony Cordesman, an analyst at the Center for Strategic and International Studies in Washington.
The biggest risk is that Saddam would retaliate with biological or chemical weapons. That might happen even if America does a slow military buildup, said Baker, who along with others considers this the critical danger.
In any surprise attack, the keys would be:
-- Air power:
The United States could launch strikes off aircraft carriers in the Red Sea and Persian Gulf, and from land bases in Kuwait, Qatar, Oman, Diego Garcia and possibly Turkey. The military also might try, early on, to seize airfields in western Iraq itself and also use Kurdish-controlled northern Iraq.
Help from neighboring Saudi Arabia or Jordan isn't strictly needed, Cordesman said, but it would give the United States more military flexibility to have Saudi staging areas.
Jordan reiterated on Wednesday that it would not allow foreign troops to use its territory for any attack against Iraq, a position the Saudis also have publicly taken.
-- Moving troops and equipment:
Transport ships carrying heavy equipment, weapons and tanks from Guam, Diego Garcia and elsewhere could be sent to the Persian Gulf region without attracting much initial notice.
The public would learn that a large convoy was moving toward Iraq only when the ships passed through the Strait of Hormuz into the Persian Gulf, a day or so from docking in Kuwait. Other heavy equipment is stored in nearby Qatar and the United Arab Emirates.
Once in Kuwait, the ships could provide tanks to waiting U.S. soldiers.
Some 10,000-15,000 troops already could be in Kuwait through normal rotations. An additional 35,000-40,000 could be flown in quickly from surrounding bases or ships.
The U.S. military also might try to employ Iraqi opposition forces like the Kurds in the north, or dissident generals, but there are strong risks to that.
-- Stopping missiles:
The United States would try to use reconnaissance aircraft like the unmanned Predator to find and prevent Saddam from launching short-range ballistic missiles armed with chemical or biological weapons.
Najib al Salhi, a former Iraqi general opposed to Saddam, contended in a recent Washington speech that the United States could prevent such launches. But most U.S. experts call that wishful thinking.
Many Iraqi missile launchers are hidden either in hardened bunkers, or beneath sites like hospitals or garages. It's considered likely that Saddam would manage to launch at least some toward either U.S. troops or toward civilians in Israel.