As many as 129 million Americans under age 65 have medical problems that are red flags for health insurers, according to an analysis that marks the government's first attempt to quantify the number of people at risk of being rejected by insurance companies or paying more for coverage.

The secretary of health and human services is scheduled to release the study on Tuesday, hours before the House plans to begin considering a Republican bill that would repeal the new law to overhaul the health-care system. The report is part of the Obama administration's salesmanship to convince the public of the advantages of the law, which contains insurance protections for people with preexisting medical conditions.

Republicans immediately disparaged the analysis as "public relations." An insurance industry spokesman acknowledged that sick people can have trouble buying insurance on their own but said the analysis overstates the problem.

The study found that one-fifth to one-half of non-elderly people in the United States have ailments that trigger rejection or higher prices in the individual insurance market. They range from cancer to chronic illnesses such as heart disease, asthma and high blood pressure.

The smaller estimate, by Health and Human Services Department researchers, is based on the number of Americans whose medical problems would make them eligible for states' high-risk pools - special coverage for people denied insurance because of their medical history. The researchers arrived at the larger figure by adding in other ailments that major insurers consider a basis to charge customers higher prices or to exclude coverage for some of the care they need.

Using those two definitions, the study took 2008 findings, the most recent available, from a large federal survey of medical expenditures to figure out how many people had reported that they were bothered by those health problems, had visited a doctor for them or had been at least temporarily disabled because of them.

The study is laced with reminders about provisions of the 2010 Patient Protection and Affordable Care Act - as the health-care law is formally known - that are designed to eliminate insurance problems for such people.

The most significant is scheduled to take effect in 2014, when the law will, for the first time, forbid insurers to charge sick patients more or reject sick applicants. Last year, two smaller changes took effect: a rule that insurers cannot reject sick children, and temporary subsidies until 2014 for a federal high-risk pool and new state ones. In their early months, the pools have not proved popular.

"Americans living with pre-existing conditions are being freed from discrimination in order to get the health coverage they need," HHS Secretary Kathleen Sebelius says in a statement, to be released Tuesday, in which she argues that repealing the law would leave such people unprotected.

Told about the new analysis, Robert Zirkelbach, a spokesman for America's Health Insurance Plans, the industry's main lobbying group, said: "Look, we've long supported reforming the individual insurance market so that everybody can have access to health-care coverage, regardless of their preexisting medical conditions. But this report exaggerates the number of people who are impacted."

Most of the Americans included in the figures, Zirkelbach said, currently have insurance. They would be at risk, he said, only if they needed to change coverage and buy it on their own. People who get insurance through their jobs are guaranteed coverage, he noted.

A Republican House aide, speaking about the report on condition of anonymity because it was not yet public, said, "When a new analysis is released on the eve of a vote in Congress, it's hard to view it as anything but politics and public relations."

The House's new GOP leaders plan to begin debate Tuesday on a bill that would repeal the health-care law in its entirety. The vote is set to conclude on Wednesday.

"Defenders of this law are setting up a false choice by implying we must choose between [the law] in its entirety or no benefits at all for individuals with preexisting conditions," the aide said. "Republicans have consistently advocated for coverage options for individuals with preexisting conditions."

Leading Republicans, including the party's 2008 presidential nominee, Sen. John McCain (Ariz.), have been proponents of high-risk insurance pools. It is less clear what the GOP position is on the part of the law that will end insurers' ability to deny coverage or charge more if people are sick. A GOP alternative last year to the Democratic legislation was silent on the issue.

Another Democratic analysis, released last fall by Rep. Henry A. Waxman (D-Calif.), then the chairman of the House Energy and Commerce Committee, said that between 2007 and 2009, the nation's four largest private health insurers denied coverage to about 650,000 people based on their medical history.

The new report says that, of those Americans who are uninsured, 17 percent to 46 percent have medical conditions, depending on the definition used.

Such health problems, the study found, are especially common among adults ages 55 to 64 - a group long recognized as a problem spot in the health-care system, because people of that age tend to have higher medical expenses but do not yet qualify for Medicare.