Barack Obama expected to name John Kerry as secretary of state

President Barack Obama has decided to nominate senator John Kerry as the next secretary of state, to replace Hillary Clinton, according to two major news outlets. An announcement is possible before Christmas.

Kerry, a senior ranking Democrat who ran for the White House in 2004, emerged as favourite after the US ambassador to the United Nations, Susan Rice, withdrew from contention on Thursday. That speculation hardened over the weekend, with both ABC and CNN reporting that Obama had opted for Kerry.

His appointment would require Kerry to resign from the senate, with a special election having to be held by the summer. His replacement as Democratic candidate would almost certainly face a strong challenge from the former Republican senator Scott Brown, who lost the other Massachusetts seat to Elizabeth Warren in November.

Kerry, who is currently chairman of the Senate foreign relations committee, is in the classic diplomatic mould, with decades of experience in foreign policy and a desire to be engaged in the big issues of the day, from Syria to Iran. While Clinton also wanted to be involved in the major issues of the day, she also pursued single, universal issues such as championing women's rights.

Conventional thinking in Washington has it that Clinton has never been close to Obama and has tended to be excluded from decision-making on major issues such as Iran and the Israeli-Palestinian conflict, though she played an important part in shaping policy on Libya. Likewise, Kerry is not thought to be part of Obama's inner circle, but he will harbour hopes that he will not be left on the sidelines, having been used by the president as an envoy to resolve awkward issues in Afghanistan and Pakistan. Unlike Rice, Kerry, as a senator, can expect a smooth nomination process.

The vacancy in Massachusetts could prompt infighting among Democrats for a plum senate seat in what is normally one of the safest Democratic states. But Brown's surprise 2010 victory in the state, following the death of Ted Kennedy, offers the Republicans hope for another election upset.

The special election would have to take place within 145 to 160 days of Kerry's resignation. The winner would then complete the remaining year and a half of Kerry's term, before facing re-election in 2014.

Another place in Obama's diplomatic and national security team could be filled by the appointment of a former Republican senator, Chuck Hagel, as defense secretary, a move that would help Obama portray his cabinet as bipartisan. But Hagel's appointment could provoke a backlash from some pro-Israeli groups.

Hagel has long been an advocate of the US taking a more balanced approach towards the Israelis and Arabs. He is also a passionate advocate of direct US negotiations with Iranian leaders over the nuclear issue – during the Bush presidency he publicly opposed air strikes against Iranian nuclear facilities. Hagel has emerged as one of the frontrunners to replace Leon Panetta at the Pentagon.

"I don't know who else is in contention but he is a contender," said a source who knows Hagel.

Bloomberg News disclosed on Thursday that Hagel had been vetted for the job.

The source added: "He has met with many people in the White House about this." There have been three meetings, including one with Obama on 4 December, it is thought.

Hagel, a former infantry sergeant who saw combat in Vietnam and was awarded two Purple Hearts, has often adopted positions on foreign policy that put him at odds with his Republican colleagues, including opposition to the 2003 Iraq war. Since leaving the Senate in 2009, he has been co-chair of the president's intelligence advisory board.

Other contenders for the job include Michele Flournoy, the former under-secretary for defense.