The Bush administration Thursday proposed stronger job protections for U.S. doctors and other health care workers who refuse to participate in abortions because of religious or moral objections.

Health and Human Services Secretary Michael Leavitt said that health care professionals should not face retaliation from employers or from medical societies because they object to abortion.

"Freedom of conscience is not to be surrendered upon issuance of a medical degree," said Leavitt. "This nation was built on a foundation of free speech. The first principle of free speech is protected conscience."

The proposed rule, which applies to institutions receiving government money, would require as many as 584,000 employers ranging from major hospitals to doctors' offices and nursing homes to certify in writing that they are complying with several federal laws that protect the conscience rights of health care workers. Violations could lead to a loss of government funding and legal action to recoup federal money already paid.

Abortion rights supporters served notice that they intend to challenge the new rule.

"Women's ability to manage their own health care is at risk of being compromised by politics and ideology," Cecile Richards, president of the Planned Parenthood Federation of America, said in a statement.

The group, which had complained that earlier drafts of the regulation contained vague language that might block access to birth control, said it still has concerns about the latest version.

"Planned Parenthood continues to be concerned that the Bush administration's proposed regulation poses a serious threat to women's health care by limiting the rights of patients to receive complete and accurate health information and services," Richards added.

But Leavitt said the regulation was intended to protect practitioners who have moral objections to abortion and sterilization, and would not interfere with patients' ability to get birth control or any legal medical procedure.

"Nothing in the new regulation in any way changes a patient's right to any legal procedure," he said, noting that a patient could go to another provider.

"This regulation is not about contraception," Leavitt added. "It's about abortion and conscience. It is very closely focused on abortion and physician's conscience."

The 36-page rule seeks to set up a system for enforcing conscience protections in three separate federal laws, the earliest of which dates to the 1970s. In some cases, the laws aim to protect both providers who refuse to take part in abortions and those who do.

The regulation is written to apply to a broad swath of the health care work force, not doctors alone. Accordingly, an employee whose task it is to clean the instruments used in a particular procedure would be covered. Also covered would be volunteers and trainees.

The underlying laws deal mainly with abortion and sterilization, but both the laws and the language of the rule seem to recognize that objections on conscience grounds could involve other types of services.

The regulation would take effect after a 30-day comment period