Washington, DC (LifeNews.com) -- Supreme Court Justice Sandra Day O'Connor, the first woman appointed to the nation's highest court, announced her retirement on Friday. Her resignation opens the door for President George W. Bush to make his first appointment to the Supreme Court and paves the way for an intense political battle.

The retirement creates the first vacancy on the Supreme Court in 11 years and groups on both side of the abortion debate have been waiting for months to pounce on the extreme political debate it will cause over a nominee to replace her.

O'Connor was appointed by President Ronald Reagan in 1981 and is often seen as a deciding middle of the road vote on the court. Republicans were consistently chagrined by her decisions and say she betrayed her conservative ideological views on other political issues by strongly backing abortion.

In the 1992 Casey vs. Planned Parenthood case, which saw the court uphold some state pro-life laws, O'Connor voted with the 6-3 majority to uphold Roe v. Wade, the 1973 court decision that legalized abortion on demand. She called the infamous decision "a rule of law and a component of liberty we cannot renounce.''

"Our obligation is to define the liberty of all. We reaffirm the constitutionally protected liberty of women to obtain an abortion," she wrote.

She also cast the deciding vote in the 2000 court case that overturned a Nebraska ban on partial-birth abortions.

The Nebraska case had national implications and dozens of bans on the grisly mid-term abortion procedure were overturned as a result.

Meanwhile, a federal ban on partial-birth abortions is making its way to the high court and if President Bush replaces O'Connor with a pro-life nominee, the court may reverse its 2000 decision on the legislation.

O'Connor's retirement is not a surprise as she is one of a few judges, including Chief Justice William Rehnquist, who was on a "retirement watch" list. She has been treated for breast cancer and was to said to be ready to return to her native Arizona.

O'Connor is 75 years old and she says she expected to leave the top court before it begins its next term in October, or whenever the Senate confirms a successor.

In a resignation letter, O'Connor said it was a "great privilege" to serve on the court and she added she has "enormous respect" for its role in the political process.