On the world stage, President Obama often looks a little lonely, like a man without a friend. But then, he doesn't seem to believe he needs one.
Where some presidents prized camaraderie with other heads of state, Obama's dealings are more impersonal. Relations with China's Hu Jintao are correct. Israel's Benjamin Netanyahu, chilly. And Afghan leader Hamid Karzai? Don't ask.
"My own sense is that he doesn't really have good buds" among world leaders, said Peter Hakim, president emeritus of the Inter-American Dialogue, a think tank. "He can pick up the phone and talk to any leader and get a good response, but it's business."
Obama takes a bottom-up approach, as was clear from his recent trip to Latin America — where at every stop he took time to visit historic sites and made other gestures likely to stir positive reactions from the broader public. If the president is popular with the public in a country, White House strategists calculated, he is likely to gain more diplomatic leverage than from warm personal relations with a leader.
That approach fits within a theory of international relations that hard national interests trump personal ties.
"Friendship helps, but it's icing on the cake. The cake is national interest," said Joseph Nye, a Harvard University professor and author of the new book "The Future of Power."
Obama's old Senate staff knew at an early point that forging personal relationships wasn't the boss' forte. In the book "Game Change," the authors cite the thinking of an Obama aide that he "lacked a feel for and had little interest in … developing relationships with potential allies."
"There is some analogy between Obama's ability to do that in the U.S. Senate and his ability to do that on the world stage," said Eric S. Edelman, former undersecretary of defense for policy under George W. Bush and a former U.S. ambassador to Turkey.
The aloof style practiced by Obama is evident in the Libya crisis, where he is operating as one global leader among many, rather than drawing on personal relationships to reach a desired result.
Other presidents have spent more energy courting peers.
George W. Bush sometimes invited other world leaders for informal weekends at Camp David, the presidential retreat in the mountains near Washington. On one visit, Bush, Tony Blair of Britain and their wives settled in to watch the comedy "Meet the Parents."
After agreeing on the movie, "Laura and I knew the Bushes and Blairs would get along," Bush wrote in his memoirs.
Obama doesn't give the impression he wants another pal. His method is to sit with his counterparts in closed-door meetings and run through lists of unresolved issues.
The world may be too complex, too intertwined, for friendship to matter in any case, he has suggested.
So familiar were President Franklin D. Roosevelt and British Prime Minister Winston Churchill that the president once got a glimpse of Churchill climbing out of a White House bathtub.
Citing the historically close relationship between the two, Obama said in 2009: "If there's just Roosevelt and Churchill sitting in a room with a brandy, that's an easier negotiation. But that's not the world we live in, and it shouldn't be the world that we live in."
Obama doesn't shirk closed-door meetings with his counterparts. But when he travels, he often spends part of the trip mixing with everyday people and delivering speeches meant to influence the broader population.
He visits important national landmarks — as he did in El Salvador on March 22 when he saw the tomb of the slain human rights champion and cleric Oscar Romero. Two days earlier he kicked soccer balls with children in a Rio de Janeiro slum.
Aware that many people in the region are resentful of the U.S., Obama said in a speech in Chile on March 21 that North and South America should be "equal partners."
"Now, I know I'm not the first president from the United States to pledge a new spirit of partnership with our Latin American neighbors. Words are easy, and I know that there have been times where perhaps the United States took this region for granted," he said.
Does one style of presidential statecraft work better than another?
Edelman contends that Obama might get more cooperation in the messy dispute over the war in Libya if he had closer ties to counterparts.
"Part of diplomacy are personal relationships. It can play a role here," Edelman said, speaking of the negotiations over who would command operations in Libya.
But Nye mentions the case of Bush's dealings with former Mexican leader Vicente Fox. While the two men seemed to have a warm rapport, that proved of no value when Bush wanted Mexico's support for a U.N. Security Council resolution in 2003 authorizing military action in Iraq.
Not that Obama hasn't had troubles of his own. Consider Brazil.
A Gallup poll last year showed that befriending Obama might be in the interests of the country's new president, Dilma Rousseff. The survey found that 55% of Brazilians approved of Obama's job performance.
Yet when the U.N. Security Council voted to authorize military action in Libya on March 17, Brazil abstained.
Nor was the White House successful in persuading Rousseff to take part in a news conference with Obama during his visit to the country.
"It's not her way. She didn't do it with the president of East Timor either," a Brazilian official told a reporter.
Nicholas reported from Brasilia and Bennett from Washington.