Roman Catholic politicians who support a proposed law allowing woman to have abortions in Mexico City should no longer receive communion, the Pope said Wednesday in a statement clarifying earlier remarks.

The statement, which stopped short of saying the politicians should face formal excommunication, was issued by a Vatican spokesman, Rev. Federico Lombardi, and approved by Pope Benedict XVI.

During an earlier news conference, aboard a plane carrying the Pope to Brazil, journalists had asked him about comments by Mexico City church officials that legislators who voted last month to legalize abortion would be excommunicated.

"It's nothing new, it's normal, it wasn't arbitrary. It is what is foreseen by the church's doctrine," the Pope responded.

Lombardi, who was travelling with the Pope, said: "Since excommunication hasn't been declared by the Mexican bishops, the Pope has no intention himself of declaring it.

"Legislative action in favour of abortion is incompatible with participation in the Eucharist," he said.

Pressed by reporters about whether that meant they were excommunicated, Lombardi repeated: "No, they exclude themselves from communion."

Lombardi later issued the clarifying statement after reporters filed stories saying the Pope supported excommunicating the politicians.

Abortion law passes

The proposed law to permit abortion during the first 12 weeks of pregnancy was approved by Mexico City politicians on April 24 by a 46-19 vote, with one abstention.

While it would only apply within the capital, women could travel there to have the procedure performed.

Mexico City hospitals would be required to provide abortions and the door would also be opened to the establishment of private abortion clinics.

Federal Mexican law allows abortion only in cases of rape, if the fetus has been deemed to have severe birth defects or if the pregnancy puts the mother's life at risk.

Roman Catholic church officials in Mexico said earlier that doctors and nurses who perform abortions will be excommunicated, along with pro-abortion legislators.

About 90 per cent of Mexicans are Catholic, the largest number of any country after Brazil.

While polls show a majority of Mexico City residents support legalizing abortion, there is also significant opposition, with some groups vowing to appeal the measure to the Supreme Court.

5,000 march against abortion in Brazilia

Before the Pope's five-day visit, about 5,000 people turned out on Tuesday for an anti-abortion march in the capital, Brazilia. The procedure is legal in Brazil only in cases of rape or when a woman's life is in danger.

Pope Benedict, who visited Brazil as then cardinal Joseph Ratzinger in 1990, will celebrate several open-air masses, including a canonization ceremony for Brazil's first native-born saint, and visit a church-run drug and alcohol rehabilitation centre.

He will also meet with bishops from Latin America in a once-a-decade meeting in the shrine city of Aparecida near Sao Paulo.

During his visit, the Vatican has said Pope Benedict will deliver a tough message on poverty and crime.

He will meet with Brazilian President Luiz Inacio Lula da Silva in Sao Paulo. But a spokesman said the centre-left leader does not plan to bring up abortion or other sensitive issues, such as a government anti-AIDS program that distributes millions of condoms each year.

With files from the Associated Press