Susan Rice aggressively spearheaded President Barack Obama's foreign policy as his top diplomat at the United Nations, promoting democracy in the Middle East and tougher sanctions against Iran and North Korea.

But she dropped out of the running to be secretary of state after Republicans heaped blame on her for the Obama administration's bungled account of last September's terrorist attack in Benghazi, Libya, that killed four Americans, including a U.S. ambassador.

Rice was the face of the administration's public account of the Sept. 11 attack, which did not initially blame terrorists. Until then, she had been the front-runner for secretary of state, which requires U.S. Senate confirmation.

Her new job as Obama's national security adviser does not require Senate confirmation. The appointment is expected to be announced Wednesday.