The Republican presidential front-runner has said that if elected, he might halt purchases of oil from Saudi Arabia and other Arab allies unless they commit ground troops to the fight against the Islamic State or “substantially reimburse” the United States for combating the militant group, which threatens their stability.

He approached almost every current international conflict through the prism of a negotiation, even when he was imprecise about the strategic goals he sought.

NEW YORK — In Donald Trump’s worldview, the United States has become a diluted power, and the main mechanism by which he would reestablish its central role in the world is economic bargaining.


“If Saudi Arabia was without the cloak of American protection,” Trump said during a 100-minute interview on foreign policy, spread over two phone calls, “I don’t think it would be around.”

He also said he would be open to allowing Japan and South Korea to build their own nuclear arsenals rather than depend on the US nuclear umbrella for their protection against North Korea and China. If the United States “keeps on its path, its current path of weakness, they’re going to want to have that anyway, with or without me discussing it,” Trump said.

And he said he would be willing to withdraw US forces from both Japan and South Korea if they did not substantially increase their contributions to the costs of housing and feeding those troops. “Not happily, but the answer is yes,” he said.

Trump also said he would seek to renegotiate many fundamental treaties with US allies, possibly including a 56-year-old security pact with Japan, which he described as one-sided.

Trump faulted the Obama administration’s handling of the nuclear negotiations with Iran last year. “It would have been so much better if they had walked away a few times,” he said


But he offered only one new idea about how he would change the content of the nuclear deal: Ban Iran’s trade with North Korea.

Trump struck similar themes when he discussed the future of NATO, which he called “unfair, economically, to us,” and said he was open to an alternative organization focused on counterterrorism. He argued that the best way to halt China’s placement of military airfields and anti-aircraft batteries on reclaimed islands in the South China Sea was to threaten its access to US markets.

“We have tremendous economic power over China,” he argued. “And that’s the power of trade.” He made no mention of Beijing’s capability for economic retaliation.

Trump’s views, as he explained them, fit nowhere into the recent history of the Republican Party: He is not in the internationalist camp of President George H.W. Bush, nor does he favor George W. Bush’s call to make it the mission of the United States to spread democracy around the world. He agreed with a suggestion that his ideas might best be summed up as “America First.”

Trump explained his thoughts in concrete and easily digestible terms, but they appeared to reflect little consideration for potential consequences around the globe.

Much the same way he treats political rivals and interviewers, he personalized how he would engage foreign nations, suggesting his approach would depend partly on “how friendly they’ve been toward us,” not just on national interests or alliances.

At no point did he express any belief that US forces deployed on military bases around the world were by themselves valuable to the United States, though Republican and Democratic administrations have for decades argued that they are essential to deterring military adventurism, protecting commerce, and gathering intelligence.


Until recently, Trump’s foreign policy pronouncements have largely come through slogans: “Take the oil,” “Build a wall,” and ban Muslim immigrants, at least temporarily. But as he has pulled closer to capturing the nomination, he has been called on to elaborate.

Pressed about his call to “take the oil” controlled by the Islamic State in the Middle East, Trump acknowledged that this would require deploying ground troops, something he does not favor. “We should’ve taken it, and we would’ve had it,” he said, referring to the years in which the United States occupied Iraq. “Now we have to destroy the oil.”

Trump did not rule out spying on US allies, including foreign leaders like Angela Merkel, the German chancellor, whose cellphone was apparently a target of the National Security Agency. President Obama said the United States would no longer target her phone but made no such commitments about the rest of Germany, or Europe.

“I’m not sure that I would want to be talking about that,” Trump said.