Congress is set to break new ground in banning a specific abortion procedure.
A ban on what critics call partial birth abortion is expected to win approval in the Senate. That approval could spark a fierce legal fight affecting a woman's right to end a pregnancy.
The House approved the ban by a two-to-one margin earlier this week and Senate passage will send it on to President Bush, who has promised to sign the bill.
It would be the first ban of a specific abortion procedure since the Supreme Court legalized abortion 30 years ago.
President Clinton twice vetoed partial birth abortion bills on the grounds that they did not include exceptions to protect the health of the mother.
Passage became inevitable after Republicans regained control of the Senate in the 2002 election, giving the GOP control of the White House, House and Senate.