If confirmed by the US Senate, she will replace retiring Justice Sandra Day O'Connor, the first woman to serve on the nine-seat high court and often a critical swing vote on volatile matters that divide Americans.

Bush said Miers had devoted her life to the rule of law and the cause of justice.

"She will be an outstanding addition to Supreme Court of the United States," the president said, with her at his side in the Oval Office of the White House.

Influential

The court wields enormous influence over American life as the final arbiter of the US Constitution and ultimate court of appeal, and has ruled on issues such as abortion, the death penalty, and same-sex marriage. Justices are named for life but can step down.

O'Connor was the first woman to
serve on the court

The nomination came as Bush grappled with some of the poorest approval ratings of his presidency, battered by soaring petrol prices, the war in Iraq, and the widely criticised response to killer Hurricane Katrina.

Miers, 60, has never served as a judge, but has been a close aide to Bush ever since he was governor of Texas. She would join Justice Ruth Bader Ginsburg as the second woman on the court and third in its history.

"If confirmed, I recognise that I will have a tremendous responsibility to keep our judicial system strong and to help ensure that the courts meet their obligations to strictly apply the laws and the Constitution," she said.

Praise

Her nomination came as newly confirmed US Chief Justice John Roberts, Bush's pick to replace the late William Rehnquist, formally took up his duties as the high court opened a new session.

The president had initially nominated Roberts to replace O'Connor, who announced her retirement in July but agreed to stay on until her replacement is confirmed by the Senate, where his Republicans hold 55 of 100 seats.

Bush's approval ratings have
recently plunged

But with Rehnquist's passing after a long illness, Bush nominated Roberts for chief justice, and he easily won confirmation.

"I believe the senators of both parties will find that Harriet Miers' talent, experience and judicial philosophy make her a superb choice to safeguard the constitutional liberties and equality of all Americans," he said.

"I ask the Senate to review her qualifications thoroughly and fairly and to vote on her nomination promptly," said the president.

Abortion activists concerned

Bush paid special tribute to Miers' groundbreaking roles as the first woman hired at one of the top law firms in Dallas, Texas; the first woman to become president of that firm, and the first woman to be elected president of the Dallas Bar Association.

As a high-powered trial lawyer, Miers represented such firms as Microsoft and Walt Disney.

The largest abortion rights group in the United States, the Planned Parenthood Federation of America (PPFA), immediately expressed concern about the nomination and she must be clear about her position on abortion.