WASHINGTON -- President Barack Obama nominated John F. Kerry, the five-term Democratic senator from Massachusetts, to replace Hillary Rodham Clinton as secretary of state, but delayed naming a new defense chief amid growing criticism of the expected nominee.
Appearing with Mr. Kerry at the White House, Mr. Obama said Friday that the Senate Foreign Relations Committee chairman and 2004 Democratic presidential nominee had "played a central role in every major foreign policy debate for nearly 30 years."
"In a sense, John's entire life has prepared him for this role," the president said.
Mr. Obama picked Mr. Kerry after the wrenching withdrawal of his preferred candidate, Susan Rice, his United Nations envoy.
Mr. Kerry's nomination is likely to sail through Senate confirmation hearings, where he has strong support.
But it came as the White House struggled to pick a new secretary of defense. Aides say Mr. Obama's preferred choice is former Nebraska Sen. Chuck Hagel, a Republican. But Mr. Hagel faces mounting opposition from influential pro-Israel groups, gay activists and defense hawks.
Mr. Obama had been expected to announce both nominations Friday, and Mr. Hagel's absence in the Roosevelt Room -- and Mr. Obama's refusal to answer reporters' questions before he left -- suggested that the president may be considering other candidates. White House officials insisted that Mr. Obama has made no choice.
Mr. Kerry, 69, a highly decorated Vietnam combat veteran, later helped lead veterans opposed to the divisive war. Mr. Obama cited his military service as a special qualification.
"Having served with valor in Vietnam, he understands that we have a responsibility to use American power wisely, especially our military power," the president said. "And he knows, from personal experience, that when we send our troops into harm's way, we must give them the sound strategy, a clear mission and the resources that they need to get the job done."
The nomination risks the loss of what has been a reliably Democratic Senate seat. Democrats control the Senate but face midterm elections in two years that could narrow those numbers.
Republican Scott Brown, who lost his Senate seat in last month's election but remains popular in the commonwealth, could run again in a special election next year. Edward Kennedy Jr., son of the late senator, is among several Democrats who have indicated interest.
Ms. Rice withdrew from consideration Dec. 13 after a tenacious campaign by Republicans who said she had misled the country with her televised remarks after armed militants killed four Americans at the U.S. diplomatic mission in Benghazi, Libya, in September. Several GOP lawmakers who led the opposition to Ms. Rice, including Arizona Sen. John McCain, urged Mr. Obama to choose Mr. Kerry instead.
Mr. McCain praised the nomination Friday, but also said he intends to carry out his responsibility to carefully review Mr. Kerry's suitability for the post.
In his remarks, Mr. Obama acknowledged the special debt he owes Mr. Kerry. In 2004, when the Massachusetts senator was running for president, he chose Mr. Obama to deliver the Democratic National Convention's keynote address, providing the then-obscure Illinois state senator an invaluable introduction to American voters.
Republican hawks may challenge Mr. Kerry's resistance to U.S. military intervention abroad in some conflicts. And a group of Vietnam "Swift Boat" veterans who opposed his presidential campaign have vowed to voice objections again. Mr. Kerry has shared Mr. Obama's interest in trying to talk without preconditions to adversary regimes, and shares the president's desire to shift the U.S. military from the grueling ground wars of the last decade to a "light footprint" abroad.
Mr. Kerry "would much rather solve problems by negotiations and diplomacy than by war," said Jonah Blank, a former Kerry aide and South Asia specialist. "He's seen war: He knows it ain't pretty, and very often it doesn't work."
At the beginning of Mr. Obama's first term, Mr. Kerry sought to help the White House work out a broad Mideast peace deal with Syrian President Bashar Assad, a mission that continues to come under strong criticism by GOP hawks. He also acted on Mr. Obama's behalf as a diplomatic middleman in sensitive talks with Afghan President Hamid Karzai, and helped sooth relations with Pakistani leaders after a period of intense turmoil.
Mr. Kerry, whose father was a foreign service officer, has traveled widely and shown himself willing to take on the wearying drudgery of diplomacy.
Mr. Kerry's accomplishments as committee chairman include legislation he pushed, with ranking member Richard Lugar, R-Indiana, and House Foreign Affairs Committee chairman Howard Berman, D-Calif., to restructure and expand aid to Pakistan. Mr. Kerry was also an important advocate for the New Start nuclear arms reduction treaty with Russia.
Ms. Clinton has indicated she's willing to stay in her post beyond Mr. Obama's inauguration if necessary. But Mr. Kerry's selection may make that unnecessary.