ABOARD THE PAPAL PLANE (Reuters) - Pope Benedict on Wednesday warned Catholic politicians they risked excommunication from the Church and should not receive communion if they support abortion.

It was the first time that the Pope, speaking to reporters aboard the plane taking him on a trip to Brazil, dealt in depth with a controversial topic that has come up in many countries, including the United States, Mexico, and Italy.

The Pope was asked whether he supported Mexican Church leaders threatening to excommunicate leftist parliamentarians who last month voted to legalize abortion in Mexico City.

“Yes, this excommunication was not an arbitrary one but is allowed by Canon (church) law which says that the killing of an innocent child is incompatible with receiving communion, which is receiving the body of Christ,” he said.

“They (Mexican Church leaders) did nothing new, surprising or arbitrary. They simply announced publicly what is contained in the law of the Church... which expresses our appreciation for life and that human individuality, human personality is present from the first moment (of life)”.

Under Church law, someone who knowingly does or backs something which the Church considers a grave sin, such as abortion, inflicts what is known as “automatic excommunication” on themselves.

The Pope said parliamentarians who vote in favor of abortion have “doubts about the value of life and the beauty of life and even a doubt about the future”.

“Selfishness and fear are at the root of (pro-abortion) legislation,” he said. “We in the Church have a great struggle to defend life...life is a gift not a threat.”

“ALWAYS A GIFT”

The Pope’s comments appear to raise the stakes in the debate over whether Catholic politicians can support abortion or gay marriage and still consider themselves proper Catholics.

In recent months, the Vatican has been accused of interference in Italy for telling Catholic lawmakers to oppose a draft law that would grant some rights to unwed and gay couples.

During the 2004 presidential election, the U.S. Catholic community was split over whether to support Democratic candidate John Kerry, himself a Catholic who backed abortion rights.

Some Catholics say they personally would not have an abortion but feel obliged to support a woman’s right to choose.

But the Church, which teaches that life begins at the moment of conception and that abortion is murder, says Catholics cannot have it both ways.

“The Church says life is beautiful, it is not something to doubt but it is a gift even when it is lived in difficult circumstances. It is always a gift,” the Pope said.

Only Cuba, Guyana and U.S. commonwealth Puerto Rico allow abortion on demand in Latin America. Many other countries in the region permit it in special cases, such as if the fetus has defects or if the mother’s life is at risk.

Brazil, the world’s most populous Catholic country, is mulling bringing the debate to a referendum.