Mexico City's mayor said doctors at city-run hospitals will not be allowed to refuse to perform abortions because of moral objections under a newly approved law legalizing abortion.

Marcelo Ebrard said that doctors in this overwhelmingly Roman Catholic country would have to obey the law, which went into effect Thursday and legalizes abortion in Mexico City in the first 12 weeks of a pregnancy.

"We have to serve the public, that is what the law orders us to do," Ebrard told reporters on Friday.

Ebrad, whose leftist Democratic Revolution Party supported the law, did not indicate whether doctors who did not want to perform abortions would be asked to resign.

Ebrad's comments appeared to conflict with a statement Thursday by Mexico City Health Secretary Manuel Mondragon, who said doctors could not be forced to perform abortions that strictly are elective.

In cases of rape, severe deformity of the fetus or if the mother's health was at risk, abortions have long been legal in Mexico, and doctors have been required to perform them under those circumstances, although some have defied the law.

The new law requires city-run hospitals to offer abortions, and opens the way for private clinics to do so. The text of the law, passed Tuesday by the city assembly, does not address whether doctors at those hospitals can refuse to perform the procedure.

The city apparently is still working out the procedural details of the measure, the first of its kind in Mexico. Ebrad said a list was being drawn up of facilities that would offer the service.

"We are working on this, to have a registry of all the institutions, which have to comply with standards of quality medical care," he said.

The church played a vocal role in opposing the law, and church officials have said that anyone who participates in an abortion would face excommunication, including legislators who voted for the law, doctors and nurses who perform the procedure, and the woman herself.