WASHINGTON • The American Bar Association (ABA) has called for postponing a vote on Judge Brett Kavanaugh's nomination to the Supreme Court until sexual assault allegations made by Dr Christine Blasey Ford and others are investigated by the FBI.

The request was made in a letter from the association's president, Mr Robert Carlson, to the Senate Judiciary Committee's chairman, Senator Charles Grassley, and Senator Dianne Feinstein.

It followed a day of emotional and at times painful testimony on Thursday, which included Dr Ford's allegations of sexual assault by Mr Kavanaugh at a party 36 years ago and his angry denial of the encounter.

The ABA advocated that senators vote on Mr Kavanaugh's nomination "only after an appropriate background check into the allegations made by (Dr Ford) and others is completed by the Federal Bureau of Investigation", the letter said.

The call for a pause is significant not just because of the association's clout in the legal community, but because an ABA committee had said unanimously a month ago that Mr Kavanaugh was "well qualified" for the Supreme Court, its highest possible designation.

Judge Kavanaugh and his supporters had noted that distinction in arguing for his nomination to be approved by the Senate.

The request for a probe was made out of respect for the rule of law and due process, Mr Carlson wrote.

"The basic principles that underscore the Senate's constitutional duty of advice and consent on federal judicial nominees require nothing less than a careful examination of the accusations and the facts by the FBI," he wrote.

"Each appointment to our nation's highest court... is simply too important to rush to a vote," the letter said.

Proceeding "without conducting additional investigation would not only have a lasting impact on the Senate's reputation, but it will also negatively affect the great trust necessary for the American people to have in the Supreme Court".