April 14, 2008  -- Sen. John McCain, R-Ariz., the presumptive Republican presidential nominee, seemed to give a thumbs down to bipartisan legislation that would greatly expand educational benefits for members of the military returning from Iraq and Afghanistan under the GI Bill.

McCain indicated he would offer some sort of alternative to the legislation to address concerns that expanding the GI Bill could lead more members of the military to get out of the service.

Both Democratic presidential candidates — Sens. Barack Obama, D-Ill., and Hillary Clinton, D-N.Y., — have signed on as co-sponsors, and the bill has gained bipartisan support from 54 senators on Capitol Hill in addition to Webb. A vote on the proposal is expected before the summer.

But the bill, which would dramatically increase educational compensation for American troops, has run into some unexpected resistance, both at the Pentagon and now from McCain, who has remained silent on the issue, saying he had not studied the bill close enough.

Pressure had mounted on McCain to support the bill — a veterans group, which backs the legislation, delivered a petition to McCain's Senate office, signed by 30,000 veterans.

Officials in charge of Pentagon personnel worry that a more generous and expansive GI Bill would create an incentive for troops to get out of the military and go to college.

And while that might be great for the individual troop, it could be bad for the military, which is already under stress after more than five years fighting two wars.

On his campaign plane this afternoon, McCain said he and allies in the Senate are working on an alternative to the bill, but would only support something that included incentives to stay in the military.

"We are working on proposals of our own — I'm a consistent supporter of educational benefits for the men and women of the military," McCain said. "I want to make sure that we have incentives for people to remain in the military as well as for people to join the military. ... I've talked a lot about veterans' health care, so we'll continue to talk about those issues and how to care for vets. I know I can do that, having been one."

That is unlikely to sit well with Virginia Democrat Jim Webb, like McCain, a Vietnam vet, who has made the GI Bill legislation his personal crusade. It was the first legislation Webb introduced after arriving on Capitol Hill after the 2006 elections.

When he was a decorated war veteran, just back from Vietnam, in exchange for his service, U.S. taxpayers gave Webb a full ride tuition, housing and living expenses all covered under a different program in place for wounded veterans that was distinct from the GI Bill. Webb received his law degree at Georgetown Law School in the 1970s.

The schooling, courtesy of Uncle Sam, led to Webb's career as Navy secretary, novelist and now senator.

The schooling led to Webb's career as Navy secretary, novelist and now senator.

It's a different story for Matt Flavin, a first-year Georgetown law student today. He might go on to great things, but he'll have a bigger tab to pay when he does it. The government paid for all of Webb's law school, but for Flavin, who got out of the military in August and enrolled at Georgetown, the check that arrives every month at the run-down group house where he lives, is for a little over $1,100 — about 6 percent of what it costs in tuition, books and living expenses at the private school. The benefit is smaller for members of the National Guard and Reserve.

It is a big disparity, and one of the first things Webb pledged to do when he was elected to the Senate in 2006 was push for a more generous GI Bill to give soldiers, sailors, airmen and marines the same kind of benefit that put him through law school.

Since arriving on Capitol Hill, Webb has drummed up support from 54 senators, including Republicans like John Warner of Virginia, and Chuck Hagel of Nebraska, both beneficiaries of the GI Bill. Another co-sponsor is Sen. Joe Lieberman, I-Conn., who usually sides with McCain where it comes to the war and the military.

Webb is not suggesting that the government pay for everyone in the military to go to private college. He would more than double the GI Bill benefit for veterans of the wars in Iraq and Afghanistan, offering a living stipend of about $1,000 depending on where the veteran lives, and pay the equivalent in tuition of the most expensive state school in the veteran's home state.

It would also give benefits to members of the National Guard and Reserve, who, while they are often deployed overseas, do not enjoy the same benefits as regular troops. The annual cost would be, according to Webb, somewhere between $2.5 billion and $4 billion annually.

Flavin joined the military out of patriotism shortly after 9/11, went to Officer Candidate School and, over the next five years, served tours in Bosnia, Afghanistan and with Naval special forces in Iraq.

While he did not join the military specifically to get benefits from the GI Bill and does not think most troops do, Flavin supports the legislation.

"We owe them something," Flavin said of his comrades. "They've given life, limb, everything there is to give. The people who bore the most pain and suffering are the people who could use these benefits."

At Georgetown, where tuition alone is $39,390 per year for a full-time student, the GI Bill makes a dent, but not a very big one. Figures compiled by Webb's office say the GI Bill covers about 11 percent of the more than $55,000 it costs to attend Georgetown Law School, buy books and live.

President Bush, in his State of the Union address this year, suggested not expanding the GI Bill benefit for current soldiers, but making it easier for them to transfer the current benefits to family members.

The original GI Bill provided a college education to the wave of veterans returning from World War II. It was scaled back in 1956 after nearly 8 million World War II veterans had benefited from it. Since then, the GI Bill has changed several times. The current Montgomery GI Bill was enacted in 1985 and, according to Bush and Gilroy should remain distinct from the World War II version because the military is now an all volunteer force and the GI Bill is a tool used both for the recruitment and retention of qualified troops.

ABC News' Bret Hovell contributed to this report.