In his most extensive remarks on the future of the American military, Sen. John F. Kerry said here Thursday that he would expand the active-duty Army by 40,000 soldiers, including a doubling of U.S. Special Forces; speed development of new technologies and equipment to meet threats posed by terrorist networks; and better integrate the National Guard into the nation's homeland security strategy.

The Democratic presidential candidate said that, to cover part of the cost of his proposals, he would cut back current funding for a national missile defense system, which he characterized as "the wrong priority" at a time when the nature of the threats has changed.

Kerry repeated his charge that the Bush administration has instituted a "backdoor draft" to deal with a military stretched thin by deployments in Iraq and Afghanistan, and pledged as president to expand and transform the armed services to handle more effectively the unconventional threats of the 21st century.

Kerry seized on Wednesday's Pentagon announcement that it will extend tours of duty for thousands of troops whose units may be heading to Iraq and Afghanistan, part of the administration's effort to deal with a much higher level of violence than it had anticipated.

"From Day One, this administration has been obsessed with threats from other states, instead of opening their eyes to the perils of the new century: terrorist organizations with or without ties to rogue nations and failed states, entities that can become their sanctuaries," Kerry said in a speech at the Harry S. Truman Presidential Museum and Library. "These are the enemies our military is facing, and this is where we must train, arm and equip our military to win."

It was the Massachusetts senator's third major address on foreign policy in a week. He combined strong rhetoric designed to reassure voters that he would be a capable commander in chief with criticism of President Bush's policies aimed at casting himself as a more forward-looking military leader.

As part of Thursday's program, Kerry advisers announced a military advisory panel for the campaign that includes two former chairmen of the Joint Chiefs of Staff, retired Army Gen. John M. Shalikashvili and retired Navy Adm. William J. Crowe Jr.; a former director of central intelligence, retired Navy Adm. Stansfield Turner; and retired Army Gen. Wesley K. Clark, who challenged Kerry in the primaries.

Bush campaign spokesmen challenged Kerry's diagnosis and his commitment to a strong military, with Sen. Mitch McConnell (R-Ky.) describing Kerry's reference to a "backdoor draft" as "absurd." The Bush officials pointed to Kerry's past positions in opposition to some major weapons programs and upbraided him for campaigning in Florida on Wednesday rather than returning to the Senate to vote for a $25 billion appropriation for troops in Iraq and Afghanistan, which passed 95 to 0.

Asserting that U.S. forces "are stretched too thin," Kerry said in his speech that the administration has mismanaged the war in Iraq and that those U.S. forces and their families are paying the price.

"The administration's answer has been to put a Band-Aid on the problem," he said. "They have effectively used a 'stop-loss' policy as a backdoor draft. They have extended tours of duty, delayed retirements and prevented enlisted personnel from leaving the service."

Kerry said the Pentagon announcement marks just one more mistake by an administration that he said has failed to adapt to new threats posed since the attacks of Sept. 11, 2001.

"We went into Iraq with too few troops to prevent looting and crime, to maintain security, fundamental order, to secure nearly a million tons of conventional weapons now being used against our troops," he said. "We failed to build alliances and squandered the opportunity to generate wider support inside Iraq, in the Arab world and among major powers so critical to every effort we have made through the last century. These mistakes have complicated our mission: a stable Iraq with a representative government secure in its borders."

Kerry likened the challenges facing the next president to those that confronted Truman at the end of World War II when the world was challenged by a nuclear threat from the Soviet Union and the task of rebuilding a shattered Europe. "Today, in the post-9/11 world, we stand at another historic crossroad," he said. "We must change if we are to meet and defeat the danger." He added that the threats of the 21st century cannot be defeated "with a military from the last one."

Kerry earlier had proposed expanding the active-duty Army by 40,000 troops, but went further Thursday in detailing that and other recommendations. He said the 40,000 additional troops eventually could help relieve the burden on current active-duty, reserve and National Guard forces.

Kerry also said he would reshape U.S. forces by expanding the kinds of units required in post-conflict environments such as that in Iraq, saying he would add civil affairs, military police, combat support and psychological operations units.

Kerry said current forces -- and their families -- are so exhausted and burdened that "we are in danger of creating another hollow Army," a reference to the reduction in capability and morale that followed the Vietnam War.

He criticized the administration for not providing the forces in Iraq with all the equipment they need. "As president, I will see to it that we don't have to have bake sales and bargain-basement sell-offs, yard sales by parents and buy on the Internet to supply the troops of the United States of America."

The Democratic candidate offered few details to explain how he intends to speed the development and use of advanced technology, from communications gear to precision weapons.

A Kerry adviser estimated that the expanded force levels would cost $5 billion to $8 billion a year, but said Kerry intends to make his transformation budget neutral. The candidate singled out missile defense, a priority of the Bush administration, as a major target for cuts. "We must build missile defense," he said, "but not at the cost of other pressing priorities."

Focusing on the National Guard, Kerry said Bush's decision to send Guard forces to Iraq has undermined homeland security. "Sending thousands of National Guard members to Iraq has actually weakened our ability to defend our own country," he said.

Sen. John F. Kerry (D-Mass.) hugs former senator Jean Carnahan (D-Mo.) before speaking at the Truman Museum in Independence, Mo.