Donald Trump’s unorthodox campaign is causing growing anxiety over how U.S. trade, military and diplomatic policies would change if he were elected president, according to ambassadors from six continents.

Diplomats from many of the United States’ closest allies said there has not been a U.S. election since World War II in which representatives of foreign nations have felt so completely cut off from a leading presidential candidate or so unsure of his view of foreign policy.

“Scary. That’s how we view Trump,” said one ambassador whose country has a close relationship with Washington. “Could we depend on the United States? We don’t know. I can’t tell you how the unpredictability we are seeing scares us.”

The ambassador declined to be identified, as did most of the dozen current or recent ambassadors to the United States interviewed for this article. They said they did not want to alienate a potential future president or his supporters — nor appear to be meddling in U.S. politics. At the same time, they said, every nation in the world has a lot riding on who ends up in the White House.

More than 180 countries maintain embassies in Washington. A key aspect of an ambassador’s job is to report home on emerging U.S. policy shifts and cultivate working relationships with the White House and those who might be in the next administration.

Donald Trump had a good night on March 15, but polls show Republican party isn't entirely behind the GOP front-runner. (Peter Stevenson/The Washington Post)

Riordan Roett, a professor at Johns Hopkins School of Advanced International Studies, said there is “deep concern” among ambassadors that “no one can even name a foreign-policy adviser to Trump.”

Five times recently, worried ambassadors have turned to Roett at meetings and asked, “Who would Donald Trump pick as his secretary of state?”

No one has an inkling, said Roett, who directs the school’s Latin American program.

Trump has been repeatedly asked to name his list of foreign-policy advisers, but as of yet he has not.

Trump was asked on MSNBC’s “Morning Joe” this week to name his advisers on international issues, and the businessman said he primarily keeps his own counsel: “I’m speaking with myself, number one, because I have a very good brain and I’ve said a lot of things. . . . I know what I’m doing, and I listen to a lot of people, I talk to a lot of people, and at the appropriate time I’ll tell you who the people are. . . . But my primary consultant is myself, and I have a good instinct for this stuff.”

The real estate mogul’s campaign did not immediately respond Thursday to The Washington Post’s request for comment.

What Trump has said about trade and foreign policy has made many nervous.

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He has talked about banning Muslims, rejecting refugees and deporting millions of undocumented immigrants back to Mexico and Central America. In nearly every speech, Trump promises to unravel trade deals and other pacts negotiated by past presidents, including the North American Free Trade Agreement, or NAFTA, which has been in place for more than two decades.

Trump has insulted allies, saying German Chancellor Angela Merkel is “ruining Germany,” and he has praised authoritarian Russian leader Vladimir Putin. He has said derogatory things about a slew of American trading partners, including China, and some of its closest allies: Mexico, Britain, France, Japan and Saudi Arabia. Yet his popularity has only grown.

Several ambassadors said they found it troubling that Trump’s bashing of foreign countries and leaders seems to be a key part of his appeal to many American voters.

Two European ambassadors said a reason they had not reached out to Trump is that they were worried that he would make the overture public and use it to score political points.

While they both said it was important to have a relationship with leading candidates who could become president in January, they were ambivalent about reaching out to Trump — at least at this point.

“Given his positions, do we even want to have anything to do with this guy?” one said.

“Ambassadors are very hesitant to say what they are thinking, but I can tell you that they are a little bit stunned,” said Selwa “Lucky” Roosevelt, who as chief of protocol for the United States served in the State Department as a liaison between ambassadors and the U.S. government.

Said one European ambassador: “You listen to him at the debates and what he says is unsettling — he is promising to change things from one day to the next. A lot of us thought he couldn’t possibly be the nominee. Now suddenly people are talking about a brokered convention and that anything is possible in 2016 in America. The uncertainty is very, very scary.”

One ambassador from Asia said that he had been sending classified cables back home for months saying Trump had a strong following of disenfranchised, white voters but could not win.

His memos no longer say that.

Instead, he focuses on the likely showdown in November between extremes: Hillary Clinton, a former secretary of state who is especially well known to world leaders, and a businessman who is largely a mystery to them.

Ambassadors also seek out major supporters, donors or advisers to learn more about significant candidates. But Trump is a billionaire who is funding his own campaign. And many ambassadors said no one is certain who his advisers are outside a tight circle of campaign operatives.

Kim Beazley, who until January was the Australian ambassador to the United States, said it matters greatly to the world who is in the White House. “America has impact on every conceivable international problem and issue,” he said.

“We get it that we have no right to have a salient opinion on U.S politics — it’s America’s business,” Beazley said.

But, he said, given the effect the president of the world’s superpower has on other countries, it only makes sense that diplomats are trying to figure out whether Trump is serious about his “absolute statements” or might moderate his positions if elected.

When Trump says he would “bomb the sh-- out of” the Islamic State, supports waterboarding and even harsher tactics, and says he has no problem killing the family members of militants, many diplomats wonder whether he is just playing to angry voters or signaling that he would actually pursue a more belligerent U.S. foreign policy.

Even when pressed, Trump speaks about foreign policy in vague generalities, saying he has hammered out business deals for his hotels and golf courses around the world and would use his negotiating skills to get “far, far better deals” and a “win” for the United States when dealing with China, Mexico and other top trading partners.

“In the past when candidates said extreme things, there always has been some seasoned, experienced adviser you could talk to, or who would speak out to soften what was said. This is not the case with Trump,” said an ambassador from South America.

Stuart Holliday, president of the Meridian International Center, a nonpartisan group that offers a platform for diplomats to exchange ideas, said that many countries consider their ties with the United States to be their most important bilateral relationship.

He said that many ambassadors are so concerned about the political mood of the country that they are traveling to Iowa, Texas and other states to get a better sense of it. While they have seen populist movements in other countries, Holliday said, “they are not used to seeing such a volatile situation in this country.”

When Barack Obama was nominated in Denver in 2008, more than 100 ambassadors attended the convention to see the selection of the first African American nominee.

This year, analysts expect even more to attend this summer — on the Democratic side to see an expected nomination of the first female at the top of a presidential ticket, and on the Republican side to try to gain more insight into the phenomenon of Trump.

“We had such appreciation for your system when Barack Hussein Obama was elected,” said one Middle Eastern ambassador. “Hussein was his middle name. Hussein! He was black. We so admired that America could do something like that. Now you have a candidates who doesn’t want Muslims.”