WASHINGTON - He's not president, a cabinet member, or ambassador, but Sen. John Kerry (D., Mass.) has ascended to the unofficial role of President Obama's global adviser on issues that could reshape the nation's image around the world.

Mediating Afghanistan's election vaulted Kerry from the prominent chairmanship of the Senate Foreign Relations Committee into the most exclusive circle around a new president who is juggling various domestic and foreign-policy matters. Beyond policy, Kerry knows how Washington works.

Kerry and Obama also share a political pedigree. Both were mentored by Sen. Edward M. Kennedy (D., Mass.), who died in August.

"Obviously, Sen. Kerry is somebody who has a broad range of experience and an in-depth knowledge of issues, ranging from energy and climate change to health care to foreign policy," White House press secretary Robert Gibbs said. "I think it's that experience and insight that [Obama] certainly greatly values."

That last bit cannot be overstated. Obama debuted on the national stage at the 2004 convention at which Democrats nominated Kerry to challenge George W. Bush's bid for a second term. Obama's speech electrified the party and the convention. It was the first time many Americans had heard of the young Illinois state senator.

"I'm here because of you," Obama wrote Kerry on the day he was sworn in as president. The note is framed and hangs on Kerry's Senate office wall.

Now, Obama is leaning on Kerry, 65, to help shape his foreign policy. The two men met at the White House yesterday just hours after Kerry returned from Afghanistan, where he played a crucial role in persuading President Hamid Karzai to accept a runoff after a fraud-plagued election.

Kerry said he told Obama it would not make "common sense" to decide whether more U.S. troops should go to Afghanistan without knowing the election results.

He brushed off a question about how it felt to be the de facto secretary of state.

"That's an unfair characterization," he said. "I don't think it's appropriate, de facto whatever whatever." He called his participation in the talks an act of luck, in that he was in the region at the time on a fact-finding mission.

Secretary of State Hillary Rodham Clinton, Kerry said, "embraced" and encouraged his role in what became intensely personal and emotional talks with Karzai. Kerry said he was in touch with Clinton constantly while there.

"I thought it was important that I not take steps in some freelancing way," Kerry said. "She encouraged me to stay at it and to stay engaged in it, and I think we worked as an effective team."

Still, observers said, Kerry's role as a presidential adviser on so many major issues is unusual. Earlier this year, for example, Kerry helped reopen a U.S. dialogue with Syria in a meeting in Damascus for President Basher al-Assad.

David Gergen, director of the Center for Public Leadership at Harvard, said that traditionally the Foreign Relations chairman "stays at home and goes quietly on fact-finding missions.

"It's extremely rare that any president calls on an individual outside the executive branch to do as much representative work and diplomacy as Sen. Kerry," said Gergen, who was an adviser to four presidents.

If Clinton leaves her position, Gergen added, Kerry "would be on everyone's short list and probably right at the top of it as a potential successor."

Kerry already has his hands in so many international issues that it's easy for some to forget he is not part of the Obama administration.

Earlier yesterday, Gibbs slipped during an off-camera briefing and called him "Secretary Kerry."