After repeated attacks by Vice President Gore over his far-reaching health care plan, Bill Bradley punched back today, accusing his Democratic rival of retreating from fundamental changes to the nation's health insurance system that he once had supported.

"In the case of health care, Al Gore decided it wasn't worth standing and fighting," Bradley said in what he had billed as a major health policy speech. "He abandoned that fundamental Democratic principle of basic health care for all Americans he had talked about so much in the campaign of 1992 and during the first two years of the administration."

Over the past few weeks the health care fight between the two men vying for the Democratic nomination has escalated into full-blown name calling. Bradley has labeled Gore "timid" and today, in his most pointed retort, said the vice president's attacks echo "the political opportunism of Newt Gingrich," the former Republican House speaker. Gore, for his part, has said his opponent is an irresponsible big spender who was "MIA" in previous health care battles.

Bradley's health care program would require health insurance for all children, add prescription drugs as a Medicare benefit, replace the current Medicaid system with grants to individual states and allow many more Americans to buy into the health system used by federal workers.

In his speech today to health care professionals, Bradley argued that the nation's booming economy presents a unique opportunity to provide health care to millions more Americans. "I ask you, if now is not the time, when is? The time is now," he said. "I think it is morally unacceptable that 44 million Americans, one out of four of them children, don't have health insurance."

Bradley said Gore was scared off by the abysmal failure of President Clinton's 1994 health insurance overhaul. "The lesson Al Gore learned from their health care defeat was that big, bold things can't get done in Washington, so let's look to the small symbolic things," Bradley said. Instead, he argued that health care is "a large problem that requires a large solution."

"It's not now, and never has been, a question of money--it's a question of will," Bradley continued. "When the Clinton-Gore administration took office and proposed universal health care, we had $290 billion-a-year deficits, Medicare was six years from bankruptcy, and we were spending the Social Security trust fund just to keep government running. . . . Now, six years later, we have a budget surplus, and Medicare is secure until 2015. Our economic circumstances are far better, and yet we have 5 million more people without health insurance."

Gore is promoting more modest changes including giving all children health coverage by 2005, providing prescription drugs for Medicare recipients and offering tax credits to small businesses and self-employed workers to purchase insurance.

Today, during a visit to a Washington pharmacy, Gore also promised to speed up access to cheaper generic drugs largely by curbing patent extensions on name brand prescriptions. And in a new video on his campaign Web site, Gore boldly claims his proposal is "the most dramatic step[s] toward universal access to quality health coverage."

Later, Gore reacted to Bradley's remarks, arguing that his rival's proposal would decimate Medicare and Medicaid. "He offers a flawed trillion-dollar plan that will cost the American people even more in the long run," he said in a statement.

In their back-and-forth Gore and Bradley haggled over an analysis of both plans last month by Emory University professor Kenneth Thorpe, who worked in the Clinton administration on health issues. Thorpe concluded that Bradley's plan would cost $1.2 trillion over 10 years. Today he lowered the figure by $142 billion.

Thorpe estimated that Gore would spend $312 billion to cover 12.1 million uninsured people, while Bradley's proposal would provide coverage to 15 million more. The Bradley campaign disputes Thorpe's analysis, noting that he does not factor in potential savings from modernizing many health systems.

The two camps even mocked each other's rhetoric. Bradley's "stand and fight" line today was a play on Gore's charge that the former New Jersey senator failed to "stay and fight" when Gingrich led his conservative revolution in Congress. But within hours of Bradley's speech, Gore reappropriated the phrase.

"Last month while at an event together in Iowa, I asked Senator Bradley to stand up if he wanted to have regular debates," Gore said in a statement. "Given his comments today on health care, I ask him to stand again. How about it, Bill?"

Bradley's audience today was the American Public Health Association, a largely liberal group whose leaders want a plan even bigger than his. Some argued for medical insurance for homeless people, and for illegal aliens. Victor A. Sidel, professor of social medicine from the Bronx, N.Y., wore a button saying, "We Want F.D.R. Again."

Many in the audience of doctors, nurses and other public health workers strongly favor a single-payer national health insurance program, which would amount to a complete reconfiguring of the nation's medical system.

Afterward, the group's executive director, Mohammad N. Akhter, called Bradley's plan "the very best we have seen from a politician, but we need to go beyond this."

Finley C. Campbell, a Chicago minister, said "Brother Bradley" was making a fine start. "The idea of the perfect candidate is over," Campbell said. "We must educate the candidates."

Bradley said health care must be considered broadly, to include anti-smoking programs, gun registration and better nutrition. "We have to move the whole debate to health from disease," he said as he plodded toward the exit, surrounded by supporters. Nearby, dressed in fuzzy yellow, the 7-foot Henry the Hand, Champion Hand Washer, was handing out tips for children.

Connolly reported from Washington.

CAPTION: Bill Bradley addresses health convention in Chicago. He said Vice President Gore had abandoned a Democratic principle of "basic health care for all Americans."