Kerry, the 2004 Democratic candidate for president defeated by President Bush, is noted for having the experience, gravitas and relationship-building skills that could help him as Clinton's successor.

He has traveled the globe on behalf of the Obama administration to mend frayed relationships. Most notably, he traveled to Pakistan amid deteriorating relations from a series of incidents, including the raid that killed al Qaeda leader Osama bin Laden.

Obama has praised the senator's "extraordinarily distinguished Senate career" and military service in the Vietnam War. He said Kerry has earned the respect and trust of his Senate colleagues, both Democrats and Republicans, and the president said he's confident the Senate will swiftly confirm the nomination.

Others have echoed the praise for Kerry.

"There are very few people with greater experience over a longer period of time," said Nicholas Burns, a former career ambassador who has served every secretary of state since Warren Christopher, and was most recently undersecretary for political affairs under Condoleezza Rice. "He would be a very, very impressive choice."

"You really need someone who is a renaissance person with a tremendous range of skill, both political and substantive, with a deep reservoir of knowledge," Burns said. "You need someone who can drill several layers deep on foreign policy issues."

Kerry, 69, spent much of his childhood overseas. After graduating from Yale University in 1966, he was deployed to Vietnam as a lieutenant in the U.S. Navy. He was a gunboat officer on the Mekong Delta, earning the Silver Star, the Bronze Star and three Purple Hearts.

Upon his return home in the early 1970s, Kerry gained public recognition as the head of the group Vietnam Veterans Against the War and for his anti-war testimony before the Senate Foreign Relations Committee.

In 1972, he ran his first campaign, a losing effort for a congressional seat in Massachusetts. In 1982 he became lieutenant governor under Massachusetts Gov. Michael Dukakis. Two years later, Kerry won the U.S. Senate seat he has held for five consecutive terms.

Kerry would come to the secretary of state post with a full plate of foreign policy hot spots, including the civil war in Syria, the nuclear antics of North Korea, a looming showdown with Iran over its nuclear program, political chaos in Egypt and the rest of North Africa, and, of course, the Middle East peace process.

Like Obama, Kerry sees the benefit of reaching out to adversaries, like Iran and Syria, and giving them a chance to negotiate. At one point, Kerry spearheaded outreach efforts to Syrian President al-Assad before the administration turned on al-Assad because of his crackdown on protesters.

But he also has called for arming the Syrian opposition and for NATO airstrikes, which Obama's administration has resisted.