The Bush administration has asked the Supreme Court to reinstate a ban on "partial birth" abortions, setting up a showdown that could be decided by the president's new choice for the court.
The appeal, which had been expected, follows a two-year, cross-country legal fight over the federal law.
An appeals court in St. Louis said this summer that the ban on late term abortion is unconstitutional because it makes no exception for the health of the woman.
The Supreme Court has already scheduled arguments in November in another abortion case, involving New Hampshire's parental notification statute. That case also asks whether the state law is unconstitutional because it lacks an exception allowing a minor to have an abortion to protect her health in the event of a medical emergency.