President Barack Obama on Dec. 21 nominated U.S. Sen. John Kerry to replace Hillary Clinton as secretary of state, marking his first major step in the overhaul of his national security team on the cusp of his second term.

Obama settled on Kerry, chairman of the Senate Foreign Relations Committee and the 2004 Democratic presidential candidate, after U.N. Ambassador Susan Rice withdrew from consideration last week.

The Massachusetts Democrat is expected to win easy confirmation from his Senate colleagues.

Obama will announce Kerry’s nomination at 1:30 p.m. EST but will withhold any decision on a new defense secretary, administration officials said. The president has held off in the face of a growing backlash from critics of former Republican Senator Chuck Hagel, considered a leading candidate to replace Leon Panetta at the Pentagon.

Kerry, 69, a stalwart Obama supporter known to have long coveted the job of America’s top diplomat, will take over from Clinton, who has been consistently rated as the most popular member of the president’s cabinet.

But he will also have to pick up the pieces after a scathing official inquiry found serious security lapses by the State Department in the deadly Sept. 11 attack on the U.S. consulate in Benghazi, Libya - a report that has tarnished the final days of Clinton’s tenure.

Kerry’s nomination follows a political firestorm that engulfed Rice, seen as the early favorite for the State job, spearheaded by Republicans fiercely critical of her role in the administration’s early explanations for the Benghazi assault.

Rice, defended by Obama, said last Thursday she was withdrawing her name from consideration to avoid a potentially lengthy and disruptive confirmation process.

Kerry, known nationally through his presidential run and for his role as a Democratic power broker in the Senate, offers no such challenges.