The remarks in a charged election year come two months before the Supreme Court is expected to issue a ruling that could make or break the law.

Health and Human Services Secretary Kathleen Sebelius sought to cast the two-year-old reform law as a vital weapon against racial disparities that have long condemned U.S. minorities to higher infant mortality rates, shorter lifespans and limited access to medical services.

"The enemy is at the door and we know that they would like to dismantle these initiatives," Sebelius told the annual convention of the National Action Network, a civil rights group led by the Rev. Al Sharpton.

"Healthcare inequalities have been one of the most persistent forms of injustice," she said. "Now is not the time to turn back."

Sebelius' remarks were part of an administration campaign to promote the Patient Protection and Affordable Care Act during a turbulent election year marked by repeated calls for its repeal and a Supreme Court ruling expected in June that could declare all or part of the law unconstitutional.

Civil rights activists and the minority communities they represent are a key segment of Obama's Democratic base, whose support he could need in great numbers to stave off a Republican challenge in November, especially if the high court strikes down his signature domestic policy achievement.

Research has long shown low-income Americans, including many minorities, have significantly less access to medical care and suffer disproportionate rates of childhood illnesses, hypertension, heart disease, AIDS and other diseases.

HEALTHCARE FOR 30 MILLION UNINSURED

Designed to extend health coverage to more than 30 million uninsured Americans, Obama's healthcare reform law has become a favorite target for Republicans mainly because of an unpopular provision that requires most Americans to have private health insurance by 2014.

"We've got folks who are committed to undoing ... the important initiatives that we've made in the last few years," Sebelius told her predominantly black audience without making a direct reference to Republicans or other opponents of reform.

"Frankly, they want to go back and undo Medicare and Medicaid from the mid-1960s. They want to roll us back years and years," she added.

Medicare and Medicaid, the national healthcare programs for the elderly and poor, respectively, were created in 1965 in a period of social and civil rights reforms aimed at ending racial segregation and protecting the voting rights of minorities.

The civil rights movement of the 1960s led to monumental changes in American race relations that allowed Obama to be elected as the first black U.S. president in 2008.

The Republican-controlled U.S. House of Representatives voted last month to partially privatize Medicare and convert Medicaid to a block-grant program for states.

Sebelius called on religious leaders, health advocates and other minority leaders to help the administration educate the public about the healthcare law's benefits.

The law, which does not come into full force until January 1, 2014, has already benefited minorities by extending private insurance coverage to young adults, providing free preventive services for those with insurance and banning coverage denials for children with pre-existing conditions.

"I'm here to ask you to help," Sebelius said. "If we can begin to close the disparities in health, we begin to close disparities in other areas, too."

(Editing by Todd Eastham)

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