WASHINGTON — US envoy to the UN Susan Rice is to meet Senator John McCain on Tuesday in an apparent bid to defuse a bitter row over Libya that could hurt her chances of becoming the next secretary of state.

McCain has led Republican attacks against Rice, accusing her of misleading the public over the September 11 assault on the US mission in Benghazi, Libya that left Ambassador Chris Stevens and three other Americans dead.

"My concerns are obviously that she told the American people things that were patently false, that were not true," McCain said, confirming Tuesday's meeting, which stoked speculation Rice is the frontrunner for the nomination.

US media reported that the closed-door meeting on Capitol Hill would take place at 9.30am (1430 GMT) and that Republican senators Lindsey Graham and Kelly Ayotte would also attend, along with acting CIA director Mike Morell.

Several leading Republicans have vowed to oppose Rice's elevation to become America's top diplomat at all costs, but McCain, the party's 2008 presidential nominee, has softened his criticism in recent days.

Asked on Fox News if Rice could change his mind, McCain said: "Sure. She can. I'd give everyone the benefit of explaining their position and the actions that they took. I'd be glad to have the opportunity."

Republicans singled out Rice because she appeared on Sunday political talk shows five days after the Benghazi attack and said it was the "best assessment" of the US government that the strike was not pre-planned.

Rice said the assault appeared to have started from a "spontaneous" reaction by protesters angry at an amateur anti-Muslim video made on American soil, as had been the case in an earlier assault on the US embassy in Cairo.

President Barack Obama's administration subsequently admitted the attack had been carried out by militants linked to Al-Qaeda, and State Department and FBI probes are currently under way to find out what happened.

Rice appeared to be largely absolved of blame when the office of the Director of National Intelligence confirmed the terms "Al-Qaeda" and "terrorism" had been removed from the "talking points" brief she was given.

In his first press conference after being re-elected, Obama rushed to Rice's defense, accusing the Republicans of an "outrageous" attempt to "besmirch her reputation" and challenging them to go after him instead.

Rice broke her silence on the row last week, saying she had been the victim of "unfounded" Republican attacks.

"Let me be very clear. I have great respect for Senator McCain and his service to our country, I always have, and I always will," Rice told reporters.

"I do think that some of the statements he made about me have been unfounded, but I look forward to having the opportunity at the appropriate time to discuss all of this with him," she added.

Clinton is expected to leave office early in the New Year but Obama has kept everyone waiting to see whether he is willing to name Rice and risk a potentially tricky Senate confirmation process if Republicans dig in.

The other main contender for the role is thought to be Democratic Senator John Kerry, the influential chairman of the Senate Foreign Relations Committee who lost the 2004 presidential election to George W. Bush.