WASHINGTON -- You're afraid your cancer is back, and a health insurance company just turned you down.

Under the health care bills in Congress, you could apply for coverage through a new high-risk pool that President Barack Obama promises would immediately start serving patients with pre-existing medical problems.

Wait a second. Read the fine print. You may have to be uninsured for six months to qualify.

"If you are a cancer patient and have cancer now, you can't wait six months to go into a plan because your condition can go from bad to death," said Stephen Finan, a policy expert with the American Cancer Society Cancer Action Network. He called the waiting period in the Senate bill "unacceptable."

Advocates for people with serious health problems, as well as some insurance experts, are raising questions about one of the most important upfront benefits in the Democratic health care legislation: a high-risk pool for the medically uninsurable.

Obama proposed the pool in his September health care speech to Congress. Intended to serve the most vulnerable as a temporary fail-safe, it would stay in place until 2013. That's when insurance companies would be banned from denying coverage because of medical problems. Government subsidies would also start that year to make coverage more affordable for millions of uninsured.

Now there are concerns about the design of the high-risk pools. Besides the six-month wait, there's a more fundamental issue -- whether $5 billion set aside for the three-year program is enough. The money would be used to help people in poor health pay premiums.

Obama credits his Republican presidential rival, Sen. John McCain of Arizona, for the risk-pools idea. But when the GOP candidate proposed it in 2008, the estimated annual cost was $7 billion to $10 billion.

The Senate Finance Committee approved the six-month wait in its health care bill last month. To qualify, patients must be turned down for coverage because of a pre-existing condition and uninsured for at least six months.

"If you are somebody with cancer or a heart condition who needs immediate coverage and immediate treatment, that's not very helpful," said Karen Pollitz, a Georgetown University health policy professor.

Senate Finance staffers say the restriction is meant to prevent people from dropping more expensive coverage to take advantage of government assistance.

But the House health care bill unveiled last week by Speaker Nancy Pelosi, D-Calif., doesn't include a waiting period. Instead, it would require insurance plans who "dump" seriously ill patients to repay the federal pool. "The House provision will provide immediate relief for people with high-risk conditions who have no alternative for coverage," said Finan.

It may be easier to fix the waiting period than the financing.

When Obama embraced high-risk pools, he made what sounded like a broad promise. "For those Americans who can't get insurance today because they have pre-existing medical conditions, we will immediately offer low-cost coverage that will protect you against financial ruin if you become seriously ill," the president said.

The House and Senate followed up by setting aside $5 billion for the pools.

"It doesn't seem like it's near enough money," said Douglas Holtz-Eakin, who was a top domestic policy adviser for McCain. The McCain campaign ultimately concluded it could take as much as $20 billion a year to properly run risk pools, he said. The White House says McCain's proposal was more elaborate and not directly comparable to Obama's.

A House Republican bill released this week would provide $25 billion over 10 years for risk pools and other insurance programs for people in poor health. However, unlike the Democratic proposals, the GOP bill overall would cover far fewer uninsured.

If the Democrats' risk pool starts running out of money, the government may have to start a waiting list, raise premiums or take other unpopular measures. Congress could be asked for a bailout.

Several independent experts say concerns about the financing are valid.

"It would seem that ($5 billion) is going to be small relative to the need," said Thomas Buchmueller, a University of Michigan business professor.

Some 30 states now have risk pools for those who can't get health insurance on the private market, covering about 200,000 people at a cost of about $1 billion a year.

"This is clearly not going to be enough money to cover everybody," said Pollitz.

Insurance expert John Bertko, a visiting scholar at the Brookings Institution, said it may be possible to stretch the $5 billion, but there's a small margin for error.

Bertko said his "back of the envelope" math suggests there are about 1 million uninsured Americans in poor health, or five times the number currently covered by state high-risk pools. If all signed up for the new federal pool, it would burn through the $5 billion in a year.

However, people eligible for government benefits often fail to sign up. And if only one-third were to enroll, the budget could work.

That's cutting it close. "No doubt about that," said Bertko.