WASHINGTON — Mayor Giuliani is headed to New Hampshire today to begin a two-day rollout of his health-care plan, which will aim to expand access nationwide without the kind of government involvement that he has derided as “socialized medicine.”

The former mayor will become the first leading Republican presidential contender to lay out a detailed health-care proposal. His campaign was tight-lipped yesterday as to the specifics, but Mr. Giuliani has offered an outline of his vision on the campaign trail in recent months.

A promise to “give Americans more control over and access to health care” is no. 7 on Mr. Giuliani’s list of “12 commitments” that form the underpinnings of his White House bid. In announcing the policy pledges in June, he said his health-care plan would combine a major tax deduction of $15,000, health savings accounts, vouchers, and Medicaid and tort reform.

One item it will not include is a mandate for coverage, which at least one top Democratic candidate, John Edwards, has made a cornerstone of his own health-care plan.

Mr. Giuliani often compares Democratic proposals to “socialized medicine,” saying a mandate would “lead to government-controlled health insurance.”

One of his chief Republican rivals, Mitt Romney, signed into law as governor of Massachusetts a health plan that requires employers to provide insurance and citizens to be insured. But he has indicated that he does not support a similar mandate nationwide.

While he has not laid out a detailed proposal, Mr. Romney has said he wants the federal government to allow states the flexibility to develop their own health-care plans.

Some conservative health-care scholars have said they favor Mr. Giuliani’s plan to the one enacted in Massachusetts. His approach, they say, is similar to the proposal President Bush offered earlier this year that seeks to expand health coverage through changes in the tax code.

Senator McCain of Arizona also opposes a national mandate for health insurance; he is expected to release a full proposal in the next month or two.

Mr. Giuliani’s campaign plans to announce a team of health policy advisers today before the former mayor details his platform at a town hall forum tomorrow in Rochester, N.H.

This will be Mr. Giuliani’s fifth policy speech on a specific campaign “commitment.” He has delivered all but one in either Iowa or New Hampshire, a signal that he is serious about competing in the two early primary states, even as his campaign has acknowledged that he is better positioned in several of the larger states that are holding their primaries on February 5, including New York, New Jersey, and California.

Mr. Giuliani today will make six stops throughout New Hampshire, where he has slipped well behind Mr. Romney in the most recent polls. A CNN-WMUR survey released earlier this month showed Mr. Romney with 33% and Mr. Giuliani in second place at 18%. Mr. Romney’s 15-point margin was nearly double the lead he had in the same poll a month earlier.

The former Massachusetts governor also leads in Iowa, where he has spent considerable time and money compared to Mr. Giuliani. Mr. Romney has run several television ads in both Iowa and New Hampshire, while Mr. Giuliani released his first radio spots in the Granite State last week. He has yet to run any television ads, having spent the least amount of money among the leading GOP contenders.

Mr. Giuliani has maintained his lead over the Republican field in most national polls, although it has been trimmed by the emergence of a former Tennessee senator, Fred Thompson, who is likely to enter the presidential race after Labor Day.