In a statement, Mr. Obama took note of Mr. Kerry’s bipartisan support. “John has earned the respect of leaders around the world and the confidence of Democrats and Republicans in the Senate, and I am confident he will make an extraordinary secretary of state,” the president said.

Mr. Kerry, who is a Vietnam veteran, a former presidential nominee and the son of a diplomat, will be inheriting a difficult agenda. The conflict in Syria has killed more than 60,000 people. The international envoy on the Syrian crisis, Lakhdar Brahimi, who reported to the United Nations Security Council on Tuesday, has made no headway. Egypt is in turmoil. By Mr. Kerry’s own account, relations with Russia have deteriorated.

As chairman of the Foreign Relations Committee during Mr. Obama’s first term, Mr. Kerry was a loyal ally of the White House and served as an interlocutor with President Bashar al-Assad of Syria and President Hamid Karzai of Afghanistan, among others.

During a nearly four-hour confirmation hearing last week, Mr. Kerry demonstrated familiarity with a broad range of issues, but he did not present any new ideas on how to address them.

Hillary Rodham Clinton, whose last day as secretary of state is Friday, said at a global forum at the Newseum on Tuesday that she expected Mr. Kerry to undertake a new effort to narrow differences between Israel and the Palestinians.