WASHINGTON: Susan Rice, the embattled UN ambassador, abruptly withdrew from consideration to be the next secretary of state on Thursday after an ugly standoff with Republican senators who declared they would vigorously oppose her nomination.   

The move elevates Sen John Kerry as the likely choice to be the nation's next top diplomat when Hillary Rodham Clinton departs soon.

President Barack Obama accepted Rice's decision with a shot at Republicans. ''While I deeply regret the unfair and misleading attacks on Susan Rice in recent weeks, her decision demonstrates the strength of her character,'' he said.

Rice had become the public face of the tangled administration description of what happened in Benghazi, Libya, on Sept 11 of this year when four Americans, including the US ambassador to Libya, were killed in what is now known to have been a terrorist attack.

Rice withdrew her name in a letter to the president, saying she was convinced the confirmation process would be ''lengthy, disruptive and costly, to you and to our most pressing national and international priorities.''

''That trade-off is simply not worth it to our country,'' Rice said.

Sen John Kerry says UN Ambassador Susan Rice ''an extraordinarily capable and dedicated public servant.''

The Massachusetts Democrat, now a front-runner for secretary of state after Rice bowed out on Thursday, issued a statement praising Rice and insisting that her decision doesn't change that. He noted that she'll continue serving in the Obama administration.

Kerry said he's all too familiar with political attacks and said he's felt for Rice these past few weeks.

He said he knows Rice will continue to serve with passion and distinction.    In the 2004 presidential race, Kerry was the subject of unsubstantiated claims by the Swift Boat Veterans for Truth. The group challenged his decorated Vietnam War record.