As UCSF seeks to expand its partnership with a Catholic hospital chain, a national civil rights group says the affiliation violates the First Amendment’s prohibition against government endorsement of religion.

The admonition from Americans United for the Separation of Church and State, sent to UCSF and the University of California regents Monday, comes three weeks after 1,500 doctors and hospital employees signed a petition demanding that UC sever ties with Dignity Health, which operates religious hospitals around the state.

UCSF has affiliated with three Dignity Health hospitals since 2017: St. Mary’s and St. Francis in San Francisco, and Sequoia in Redwood City, as a way to increase capacity. Now it wants to add a fourth, Dominican in Santa Cruz.

Dignity spokesman Chad Burns has said the Catholic hospitals require UCSF doctors to sign God-affirming agreements that prohibit medical care that violate the hospitals’ religious beliefs. He said these include the “Statement of Common Values” or the more restrictive “Ethical and Religious Directives for Catholic Health Care Services,” which characterizes certain procedures, including sterilization, as “intrinsically evil.” Depending on the hospital, prohibited care can include abortions, tubal ligations, hysterectomies, sterilizations, miscarriage care, gender surgery and contraceptive counseling.

On Thursday, UCSF spokeswoman Jennifer O’Brien said the medical center’s physicians are not required to sign those precise documents. “But they do commit to provide care consistent with those value statements as part of their credentialing and privilege application to practice in Dignity Health’s hospitals. This does not impede our physicians’ ability to prescribe contraception medications at any Dignity Health hospital, regardless of its Catholic sponsorship.”

Lawyers for Americans United said the church/state problem remains.

“The University of California cannot legally enter into an agreement that binds the university, its employees, or its medical students to conform to religious doctrine in either the services that they provide or the information that they present to patients,” says the letter to UCSF chief executive Mark Laret and the regents from the group’s legal director Richard Katskee, and Ian Smith, a staff lawyer.

They asked the regents to deny UCSF’s expansion request, and to end the Dignity partnership altogether — or “alter the affiliation so that UCSF neither agrees to abide by” nor enforces the religious practices.

Laret told the regents’ health care committee this month that UCSF needs the partnership for three reasons: to provide relief for its overcrowded hospital sites, to bring UCSF’s expertise to more patients, and to replenish the money it loses by treating Medicare and MediCal patients.

And in a memo to dissenting doctors acquired by The Chronicle, Laret and other administrators said doctors who treat patients at Dignity Health hospitals “have full latitude to discuss all evidence-based options for services, including reproductive and end-of-life care, and can help more patients access any of our nationally renowned programs and services.”

But they also have to be “upfront (with patients) about what services are available in different medical facilities,” the administrators wrote. “Dignity Health hospitals do not perform elective abortions, reproductive health procedures such as IVF, or physician-assisted suicide.”

UCSF is still negotiating with Dignity Health. When a proposal is ready, it will go to the regents, a spokeswoman said.

Even so, the regents expect to discuss the expansion proposal at their May meeting in San Francisco, Chairman George Kieffer told The Chronicle.

“We certainly will consider this input along with all the other input we have received and required,” he said. “Nothing has been finalized at this point.”

Nanette Asimov is a San Francisco Chronicle staff writer. Email: nasimov@sfchronicle.com Twitter: @NanetteAsimov