US President George W Bush has chosen a conservative judge as his first nominee to the US Supreme Court.
The move has raised the prospect of partisan divisions over what is seen as the president's wish to move the court to the political right.
Judge John G Roberts, 50, currently serves on the Federal Court of Appeals for the District of Columbia.
He is described as a 'mainstream conservative', but questions have been raised about his position on abortion rights.
With Senate confirmation hearings due to take place in September, Democratic Senator Chuck Schumer, of the Senate Judiciary Committee, said not enough was known of Judge Roberts's views.
Judge Roberts worked as a clerk for the current US Chief Justice, William Rehnquist, and served as a lawyer in both the Reagan and Bush senior administrations.
He also worked in private practice, arguing 39 cases before the Supreme Court, and represented corporations opposing environmental controls.
For the past two years he has been a judge on the Federal Court of Appeals in the District of Columbia.
His nomination for that post was passed unanimously by the US Senate in 2003. An attempt to place him on the court in 1992 failed.
In 1990 he wrote an argument for the first Bush administration which said that Roe v Wade, the case which guaranteed abortion rights in the US, could be overturned.
But in the 2003 Senate hearing he described it as the 'settled law of the land'.
His position on abortion is likely to feature in the expected debate on his nomination as well as his Senate confirmation hearings.
