Agustín Castilla, a PAN deputy in the Federal District Legislative Assembly (ALDF), said his party´s local legislatures will take steps to bring the new law before the Supreme Court after it passes.

PAN federal Senate leader Santiago Creel, in the Yucatán capital of Mérida Friday for a party function, confirmed his party´s plan to mount a legal challenge of the legislation. "If there´s no life, there´s nothing else," he said.

Local legislators need 22 signatures from the 66-member ALDF to initiate a legal challenge.

There are only 17 PAN deputies, so they will need to recruit help from the minor parties and/or dissidents from the other two major parties, both of which support the legalization bill.

Together, the dominant Democratic Revolution Party (PRD) and the Institutional Revolutionary Party (PRI) have more than enough votes to decriminalize abortion in the first 12 weeks of pregnancy.

Polls also indicate the measure has strong support among Mexico City residents.

However, the Catholic Church, the PAN and other anti- abortion forces have waged a furious campaign to derail the legislation. Pro-choice city legislators say they have received death threats over the issue, and national PRD leaders asked the federal Interior Secretariat Friday to guarantee their safety during next Tuesday´s session.

Florencio Salazar Adame, undersecretary for population, migration and religious affairs at the Interior Secretariat, said no.

"It falls under the purview of the Mexico City government," he told the media. "The legislators should ask the city for protection."

Pope Benedict XVI entered the fray Friday.

Via a message from the Vatican´s secretary of state, the pope said the pending Mexico City legislation "threatens the life of the unborn."