Susan Rice, the U.S. ambassador to the United Nations and a close confidante of President Barack Obama, withdrew her name from consideration as secretary of state on Thursday in the face of what promised to be a difficult Senate confirmation battle.

Rice has drawn heavy fire from Republicans for remarks she made in the aftermath of a Sept. 11 attack on the U.S. mission in Benghazi, Libya, in which four Americans were killed, including Ambassador Chris Stevens.

"I am highly honored to be considered by you for appointment as secretary of state," Rice said in a letter to Obama. "I am fully confident that I could serve our country ably and effectively in that role. However, if nominated, I am now convinced that the confirmation process would be lengthy, disruptive and costly."

Rice's decision increases the odds that Obama will turn to another top candidate for the position, Sen. John Kerry, chairman of the Senate Foreign Relations Committee and the 2004 Democratic presidential nominee, to replace Secretary of State Hillary Clinton when she steps down early next year.

Kerry called Rice "an extraordinarily capable and dedicated public servant," in a statement released after her withdrawal was announced.

The Massachusetts Democrat, now a front-runner for secretary of state,  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.

Meanwhile, an announcement of Obama's national security team could come as early as next week. Officials say Obama is giving serious consideration to nominating former Republican Sen. Chuck Hagel as his secretary of defense to replace the current secretary, Leon Panetta.

One option discussed by White House officials is having Obama appoint Rice as his national security adviser, a position that does not require Senate confirmation. However, there has been no indication that the current national security adviser, Tom Donilon, is leaving.

Obama, in a letter to Rice, said he was grateful that she would continue on in her job at the United Nations.

"While I deeply regret the unfair and misleading attacks on Susan Rice in recent weeks, her decision demonstrates the strength of her character, and an admirable commitment to rise above the politics of the moment to put our national interests first," Obama said.

Rice has faced questions about comments she made days after the attack in Libya. Rice went on television shows to declare that the attack was a result of a spontaneous demonstration by Muslims upset over a film made in the United States that was insulting to the Prophet Muhammad.

U.S. intelligence officials have since said that militants with ties to al-Qaida affiliates were likely involved in the attacks.