As President Donald Trump attacked America's closest allies while jetting to Singapore for his summit with one of the world's most brutal dictators, foreign policy experts remain unclear on Trump's approach to world affairs.

Those close to the president interpret the Trump Doctrine in several different ways.

One top White House official characterized it as, "We're America, Bitch."

As President Donald Trump attacked America's closest allies while jetting to Singapore for his much-anticipated summit with one of the world's most brutal dictators, foreign policy experts remain largely unclear on his approach to world affairs.

But one senior White House official described the president's ideology succinctly.

"The Trump Doctrine is 'We're America, Bitch,'" the official told Jeffrey Goldberg, The Atlantic's editor in chief, in a story published Monday.

"Obama apologized to everyone for everything. He felt bad about everything," said the official, who Goldberg wrote has "direct access to the president and his thinking."

Trump, by contrast, "doesn't feel like he has to apologize for anything America does," the official said.

Another senior staffer seconded that characterization.

"The president believes that we're America, and people can take it or leave it," the staffer said.

Goldberg spoke to several of the president's close aides and friends over a period of months in an attempt to better understand Trump's "America First" doctrine, and he found a few varying interpretations.

One senior administration official described the Trump ideology as "No Friends, No Enemies," explaining that the president doesn't believe the US needs to maintain any long-term alliances, and instead should take a more transactional, short-term approach.

Another top national security official alternately described the Trump Doctrine as "permanent destabilization creates American advantage" — meaning that if the US keeps both its allies and its adversaries off balance, it will set the agenda.

Yet another friend of Trump's characterized Trump's approach as simply a reversal of President Barack Obama's international legacy.

"There's the Obama Doctrine, and the 'F--- Obama' Doctrine," he told Goldberg. "We're the 'F--- Obama' Doctrine."