Opponents of abortion in the United States plan to make their annual "March on Washington" to mark the 33rd anniversary of a Supreme Court decision that legalized abortion.

The Roe versus Wade decision was handed down on January 22, 1973. Monday's rally in Washington will include a series of speeches and demonstrations at the capitol and supreme court. President Bush will be out of town, but is scheduled to address the demonstrators by telephone.

The demonstration comes at a time when there may be a shift in the high court. Justice Sandra Day O'Connor, who is set to retire, wrote a 1992 opinion reaffirming abortion rights.

But Samuel Alito, nominated by president Bush to replace O'Connor, is seen as a possible a threat to abortion rights.

Alito has said he would approach all issues with an open mind.

Some information for this report was provided by AP and Reuters.