VATICAN CITY, HOLY SEE - The Vatican repeated Monday its opposition to abortion as French lawmakers, in a world first, were set to anchor the right in the country's constitution.

"The Pontifical Academy for Life recalls that in the era of universal human rights, there can be no 'right' to take a human life," the Vatican institution said in a statement, echoing concerns already raised by French Catholic bishops.

It appealed to "all governments and all religious traditions to do their best so that, in this phase of history, the protection of life becomes an absolute priority".

"The particular life situations and difficult and tragic contexts of our time must be addressed on the basis of a law which seeks above all to protect the weakest and most vulnerable," it added.

A congress of both French houses of parliament in Versailles was expected to vote Monday  to include the right to abortion in their country's constitution.

Abortion has been legal in France since 1975. But if lawmakers approve the new move, France will become the only country in the world to clearly protect the right to terminate a pregnancy in its basic law.

Pope Francis, head of the world's 1.3 billion Catholics, has previously described abortion as "murder".