These officials, speaking on condition of anonymity, said Britain is expected to provide as many as 25,000 troops for a total on-the-ground force of 250,000 men.
Franks briefed the Pentagon and the White House on major outlines of his plan in May. Though Bush has declined to provide any details in recent weeks, Monday, for the first time, he acknowledged being thoroughly involved in the planning.
"I'm involved in the military planning, diplomatic planning, financial planning ... reviewing all the tools at my disposal," the president said.
Bush stressed, as he has in the past, it is his firm intention to get rid of Iraqi strongman Saddam Hussein.
The president said he is a "patient person ... but I do firmly believe that the world will be safer and more peaceful if there's a regime change in that government."
The president and other officials have repeatedly said that military action is only one of the options they are looking at to impose regime change in Iraq.
According to officials who spoke to UPI, three dates are being discussed as possible times to launch the attack. The first would be before the November elections -- an option now considered the least likely, officials said.
Another would be just after the elections or January/February of next year, sources said.
Franks believes that the optimum date for an attack would be just after the November elections, one U.S. government source said, adding that the date would depend on logistical readiness.
Good weather that would allow for maximum use of U.S. air power is also a chief consideration, Pentagon officials said.
According to U.S. intelligence sources, Kuwait would be the leading staging base of the huge operation. Sources said there are already advance elements of five American divisions in Kuwait searching for sites to quarter U.S. troops and set up advanced communications and logistics networks.
Other preparatory deployment moves are taking place all over the map. For example, the 101st Airborne Division, which will be used against Iraq, is being quietly withdrawn from Afghanistan, while the 82nd Airborne, which would not be used, is being assigned to Kabul, according to Pentagon intelligence officials.
Turning day-to-day command of Afghanistan operations over to the 18th Airborne Corps, under Lt. Gen. Daniel McNeill, left Franks and the Central Command free to focus on planning the attack on Iraq, U.S. government officials said.
Sources familiar with the plans told UPI that the U.S. Army already has about a division's worth of armor and other heavy equipment pre-positioned in the Persian Gulf region, including brigade-sized depots in Kuwait, Qatar, Oman, and on ships in the Indian Ocean.
U.S. Air Force planes are already based in Kuwait, Oman, Qatar, and Saudi Arabia. In the event of the attack, more planes would operate from Turkey, which is expected to join any U.S. effort against Iraq.
Former senior Army intelligence official Pat Lang, said the United States would use U.S. facilities in Saudi Arabia, probably with a minimum of notice.
"The Saudi government would prefer not to know," Lang said.
Pentagon casualty estimates range as high as 2,000 deaths, but Lang pointed out that 5,000 deaths were predicted for Operation Desert Storm, which cost only 28 American lives.
The invasion of Iraq would occur from three directions: the north, south, and west using land- and sea-based forces. One U.S. analyst called it a "major amphibious effort" and "vertical envelopment" of Airborne and Marine Corps units, adding, "There are a dozen ways to do it."
The leading U.S. ground commander would be Lt. Gen. David McKiernan, of U.S Army Forces Central Command -- Arcent -- based at Ft. McPherson, Ga. McKiernan is formerly deputy chief of staff of military planning for the U.S. Army.
The attack would be a preemptive strike, a source familiar with the plans said. He added that the Armed Forces Staff College had done studies three years ago on U.S. preemptive strike capabilities, which are excellent. "The problem is that they cost a lot of political capital," he said.
Bush announced several weeks ago that the U.S. reserves the right to strike first under certain circumstances, essentially changing long-standing U.S. Cold War policy.
The first stage of Franks' plan would entail using electronic and other advanced military technologies "to get into Saddam's decision process" and disrupt his command and control system -- Hussein's ability to talk to his military, secret police, and security forces, including his land telephone lines, according to sources familiar with the plan.
The U.S. air strikes would use round-the-clock strikes on Hussein's palaces and his major bases of support such as the Republican Guard, the Special Republican Guard, the Saddam Fedayeen and the Baath Party, in the hope of sparking a coup.
According to Ken Pollack, deputy director of national security studies at the Council on Foreign Relations, a 1998 attack called Operation Desert Fox which attacked such targets provoked Hussein to overreact and order arrests and assassinations that resulted in Shi'a uprisings.
Anthony Cordesman, national security expert at the Center for Strategic and International Studies, noted that Desert Fox "was more of a retaliatory strike than an attempt to topple Saddam," but Pentagon officials said the planned attack would go for many of the same targets.
Cordesman said that the Pentagon expects "committed resistance" from Iraqi forces, at least at first.
But to mount such a huge invasion involves solving certain problems.
One is manpower. According to Eliot Cohen, professor of strategic studies at the Paul H. Nitze School of Advanced International Studies at Johns Hopkins University, over the decade the United States has developed a military system "very dependent on reservists."
This includes areas of intelligence, logistics, communications, and even combat support and service, he said.
After Sept. 11, Bush mobilized over 80,000 reservists and National Guardsmen to support the war in Afghanistan, with tours of duty lasting up to a year. Homeland security duties occupied the bulk of Guard troops who were used to protect U.S. forces and bases, especially those overseas. The wear and tear has reduced the readiness levels of some units, Pentagon experts said.
According to these sources, a key indicator of the administration's readiness to attack Iraq will be extending the tours of duty for the 80,000 already in service and mobilizing more reservists.
One U.S. military analyst said that a call-up of more reservists was "unavoidable" and would be done "quickly."
Larry Wortzel, military expert at the Heritage Foundation said, "Bush will not be able to run a major operation without extending tours of duty and ordering a larger call-up."
Nearly a quarter of a million National Guard troops and reservists were activated for Operation Desert Shield/Desert Storm in 1991, he said.
Next, a full-scale invasion would mean the transfer of "heavy" Army and Marine Corps divisions -- those with tanks and artillery -- from bases in Germany, Georgia, North Carolina, Texas, California, and other locations. Such transfers "would telegraph what was coming, and Saddam isn't just going to sit there," a Pentagon official said.
Some have questioned if the United States has the necessary military resources, given the war in Afghanistan.
But Mike O'Hanlon, military expert at the Brookings Institution, quoted the Bush administration as claiming that the United States still retains the capability to wage one all-out war and a second major operation, half as big, with both requiring as many as 750,000 troops in combat.
According to Pentagon figures, operations in Afghanistan and the Persian Gulf currently total about 60,000 Americans personnel while ongoing commitments in the Balkans involve another 10,000. Another 10,000 are involved with small missions in Georgia, the Philippines, and Yemen.
The United States also keeps some 37,000 troops in South Korea.
But O'Hanlon said those numbers left the United States with "a total of 10 divisions immediately available."
Because of the declining pace of air operations in Afghanistan, the rate of sorties has fallen to 50 per day, leaving plenty of assets free to topple Hussein, including unmanned aerial vehicles, aerial tankers and transports, O'Hanlon said.
"We have plenty of tactical intelligence assets in the inventory," including U-2s, a traditional, single-seat aircraft, UAVs, or unmanned surveillance aircraft, and RC-35s, a large, tanker-sized aircraft, said O'Hanlon.
In terms of critical over-flight and basing rights, Kuwait would be key. One former U.S. senior CIA official who recently talked with Kuwaiti officials reported they had expressed impatience with the fact that the Israeli-Palestinian conflict had complicated U.S. plans to get rid of Hussein.
"They want him out," the former analyst said. "They wanted to know why Kuwait was being held hostage to the Palestinian question."
Vice President Dick Cheney's 11-nation tour last March to garner support for an attack produced no public backing for the plan, but administration officials claimed that the United States will be getting plenty of crucial support privately from Arab countries who will publicly disown it.
One continuing worry is the U.S. Air Force, the most heavily stressed of all the U.S. armed services. Not only has it been playing a major part in Operation Enduring Freedom, it had been conducting reconnaissance flights over the Balkans, the Middle East, and Korea, as well as continuing Operation Northern and Southern Watch flights for the last 11 years over Iraq.
But Wortzel pointed out that the war in Afghanistan has not yet drawn on U.S. Army aviation "which ate up the Iraqis big time" in Desert Storm.
(Nicholas M. Horrock, UPI's Chief White House Correspondent, contributed to this report.)