U.N. Ambassador Susan Rice has withdrawn her name from consideration for secretary of state, Brian Williams of NBC News reports.

"If nominated, I am now convinced that the confirmation process would be lengthy, disruptive and costly -- to you and to our most pressing national and international priorities," Rice wrote in a letter to President Barack Obama, obtained by NBC News. "That trade-off is simply not worth it to our country ... Therefore, I respectfully request that you no longer consider my candidacy at this time."

With Rice out of the running, Sen. John Kerry (D-Mass.) is widely believed to be the frontrunner to replace current Secretary of State Hillary Clinton.

The Huffington Post's Sam Stein and Joshua Hersh reported earlier this month that Democrats were nervous about the prospect of nominating Kerry:

The concerns have nothing to do with Kerry's ability to handle the Foggy Bottom post. Nearly everyone agrees that he has the intellectual acumen and experience for the job.

Instead, Democrats said they worry that Republicans may be using the secretary of state fight as a roundabout way to regain a Senate seat the GOP lost this fall, when Sen. Scott Brown (R-Mass.) was defeated by Elizabeth Warren. The anti-Rice gambit, some Democrats said, has the feel of a Republican long con.

Obama released the following statement on Rice's withdrawal:

Today, I spoke to Ambassador Susan Rice, and accepted her decision to remove her name from consideration for Secretary of State. For two decades, Susan has proven to be an extraordinarily capable, patriotic, and passionate public servant. As my Ambassador to the United Nations, she plays an indispensable role in advancing America’s interests. Already, she has secured international support for sanctions against Iran and North Korea, worked to protect the people of Libya, helped achieve an independent South Sudan, stood up for Israel’s security and legitimacy, and served as an advocate for UN reform and the human rights of all people. I am grateful that Susan will continue to serve as our Ambassador at the United Nations and a key member of my cabinet and national security team, carrying her work forward on all of these and other issues. I have every confidence that Susan has limitless capability to serve our country now and in the years to come, and know that I will continue to rely on her as an advisor and friend. 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. The American people can be proud to have a public servant of her caliber and character representing our country.

(See slideshow below for more reactions to Rice's withdrawal)

Rice's potential nomination was marred by persistent Republican criticism of her response to the Sept. 11 anniversary attack on a U.S. compound Benghazi, Libya. She spoke on a number of morning shows in the wake of the attacks to defend the administration's handling of the incident, which led to the deaths of four Americans, including U.S. Ambassador Christopher Stevens. During her appearances, she described the attack as the result of a spontaneous protest stemming from an anti-Islam video, an account that was later found to be incorrect.

GOP Sens. John McCain (Ariz.), Lindsey Graham (S.C.) and Kelly Ayotte (N.H.) later emerged as her most vocal opponents, claiming that her mischaracterization of the attack was a sign that she was unfit to serve as secretary of state.

Below, Rice's notice of withdrawal:

Susan Rice Withdraws

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  • President Barack Obama

    <blockquote>Today, I spoke to Ambassador Susan Rice, and accepted her decision to remove her name from consideration for Secretary of State. For two decades, Susan has proven to be an extraordinarily capable, patriotic, and passionate public servant. As my Ambassador to the United Nations, she plays an indispensable role in advancing America’s interests. Already, she has secured international support for sanctions against Iran and North Korea, worked to protect the people of Libya, helped achieve an independent South Sudan, stood up for Israel’s security and legitimacy, and served as an advocate for UN reform and the human rights of all people. I am grateful that Susan will continue to serve as our Ambassador at the United Nations and a key member of my cabinet and national security team, carrying her work forward on all of these and other issues. I have every confidence that Susan has limitless capability to serve our country now and in the years to come, and know that I will continue to rely on her as an advisor and friend. 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. The American people can be proud to have a public servant of her caliber and character representing our country.</blockquote>

  • Sen. John Kerry (D-Mass.)

    “I've known and worked closely with Susan Rice not just at the UN, but in my own campaign for President. I've defended her publicly and wouldn't hesitate to do so again because I know her character and I know her commitment. She's an extraordinarily capable and dedicated public servant. Today’s announcement doesn't change any of that. We should all be grateful that she will continue to serve and contribute at the highest level. As someone who has weathered my share of political attacks and understands on a personal level just how difficult politics can be, I've felt for her throughout these last difficult weeks, but I also know that she will continue to serve with great passion and distinction.”

  • Sen. Lindsey Graham (R-S.C.)

  • Sen. John McCain (R-Ariz.)

    "Senator McCain thanks Ambassador Rice for her service to the country and wishes her well," the senator said in a statement from his spokesman.

  • Sen. Kelly Ayotte (R-N.H.)

    “I respect Susan Rice’s decision and appreciate her commitment to public service,” Ayotte says in a statement. “However, my concerns regarding the terrorist attack in Benghazi go beyond any one individual. I remain deeply troubled by the continued lack of information from the White House and the State Department. With four of our public servants murdered, it is critical that we get to the bottom of what happened.”

  • Rep. Barbara Lee (D-Calif.)

    “I am profoundly disappointed that Ambassador Rice, such a well qualified woman of color, would be denied the opportunity to become our next Secretary of State due to the baseless and manufactured allegations of the radical right. “I have known and worked closely with Ambassador Susan Rice for many years—on many global issues. From the genocide in Sudan to the ongoing violence in Syria, the humanitarian crisis in Haiti and the global HIV/AIDS crisis. Ambassador Rice works each and every day to advance the highest ideals of our country and would have been an outstanding Secretary of State.”