US President Barack Obama is expected to announce his nominees for secretaries of state and defense in the next two weeks, with former Republican Senator Chuck Hagel on the short list of potential choices to head the Pentagon, senior administration officials said on Tuesday.

Hagel, whose appointment would give Obama's reshuffled second-term Cabinet a bipartisan cast, met the Democratic president at the White House this week to discuss a post on his national security team. But there was no sign that Obama had decided on any of the key nominations he will put forth.

Senator Chuck Hagel leaves a news conference in Omaha, Nebraska in this March 12, 2007, file photo. [Photo/Agencies]

Obama is still deliberating whether to unveil his top national security appointments, likely to include a new CIA director, in a single high-profile package this month or to name them one-by-one, according to an administration official who spoke on condition of anonymity.

Other top contenders to replace Defense Secretary Leon Panetta are believed to include former senior Pentagon official Michele Flournoy, Deputy Defense Secretary Ashton Carter and Democratic Senator John Kerry.

Complicating matters, Obama is also deciding whether to nominate Kerry as secretary of state to replace Hillary Clinton, or to go with Susan Rice, embattled US ambassador to the United Nations.

Rice is a long-time confidante of the president, but picking her would lead to a tough Senate confirmation battle over her comments in the wake of the killing of four US citizens in Benghazi, Libya.

Kerry, chairman of the Senate Foreign Relations Committee, has coveted the job as US top diplomat and would face a much smoother confirmation process if nominated. It is unclear, however, whether he would accept the Pentagon post instead.

Reuters