President George W. Bush will announce his first nominee to the Supreme Court tonight, a lifetime appointment that could have a major impact on US social and economic issues for decades to come.
"The president has made a decision and will be announcing his nominee to the Supreme Court this evening at nine o'clock (0100 GMT)," White House spokesman Scott McClellan told reporters.
US appeals court Judge Edith Clement had emerged as an early favorite, according to Republican sources, but others cast doubt that Ms Clement was Mr Bush's choice.
Another possible female candidate is Edith Hollan Jones, who serves, like Ms Clement, on the US Court of Appeals in New Orleans.
Other possibilities mentioned in past weeks include Attorney General Alberto Gonzales, who is Hispanic, and former deputy attorney general Larry Thompson, who is black.
Among senators mentioned have been Lindsey Graham of South Carolina, Kay Bailey Hutchison of Texas, Judd Gregg of New Hampshire and John Cornyn of Texas. All are Republican.
Republican strategists said Mr Bush was leaning toward picking a woman to replace retiring Justice Sandra Day O'Connor, the first woman on the high court and a moderate conservative who often controlled the outcome on hot button issues like abortion, affirmative action and civil liberties.
Some Republicans have urged Mr Bush to name a fellow conservative. Others have urged him to choose someone who could assume Ms O'Connor's more moderate role as a key swing vote between the nine-member court's conservative and liberal wings.