The State Department long has been the key to American diplomacy abroad, while leaders in foreign capitals used well-trodden channels at Foggy Bottom to contact their counterparts in Washington.
But under President Trump's approach to foreign policy, that has changed.
"There's just no one to talk to at the State Department," said one Southeast Asian ambassador, saying the department appears irrelevant for all but minor diplomatic issues. The diplomat asked not to be named expressing his frustration.
With only a handful of senior State Department positions filled after five months in office, and no regular media briefings there to explain Trump's foreign policy, the challenge for foreign governments is exacerbated by a dearth of U.S. ambassadors.
Of the most important positions, only the U.S. envoy to China, former Iowa Gov. Terry Branstad, has been confirmed by the Senate. On Friday, the White House moved to fill another crucial vacancy, formally nominating New York Jets owner Woody Johnson as U.S. ambassador to Britain.
However, the White House has yet to submit several other key nominations. The tumult has left allies and adversaries alike scrambling to find novel ways to get the administration's ear.
Early on, Denmark tried using its national beauty pageant as a back-door channel to the White House. It asked its contestant if she had any high-level contacts, since Trump used to own the Miss Universe pageant. As far as is known, she didn't.
Some embassies have staged high-profile receptions or rented suites at the Trump International Hotel in Washington, less than a mile from the White House, in what critics say is a conspicuous effort to gain Trump's notice.
The government of Saudi Arabia, in particular, paid $270,000 to the hotel between November and February, according to filings with the Justice Department under the Foreign Agents Registration Act.
That has prompted several lawsuits alleging Trump is profiting off his presidency.
"Never in the history of this country have we had a president with these kinds of extensive business entanglements or a president who refused to adequately distance themselves from their holdings," Karl Racine, attorney general for the District of Columbia, told reporters this month when he filed a lawsuit with Maryland alleging that Saudi Arabia and Kuwait are trying to gain favor at the White House by paying top dollar at Trump properties.
The Mexican government has tried another route to improve relations with the White House.
Even as Trump railed during the campaign against Mexicans as rapists and criminals who sneaked across the border to attack Americans or steal their jobs, Mexico's then-finance minister, Luis Videgaray, was in touch with one of Trump's top advisors.
Videgaray, who is close to President Enrique Peña Nieto, established a friendship with Trump's son-in-law and advisor Jared Kushner, according to diplomats and former U.S. officials.
Knowing how unpopular Trump was in Mexico, Videgaray didn't tell the foreign minister at the time what he was doing, they said.
It backfired when Videgaray engineered a Trump visit to Mexico City last August during the campaign. Trump again insisted Mexico would pay for a border wall, embarrassing Peña Nieto, who had said they hadn't discussed it, and hijacked a news conference in the presidential palace by calling only on American reporters and ignoring the Mexicans.
Peña Nieto's popularity ratings plummeted, and Videgaray was forced to resign.
But Videgaray continued meeting with Kushner, and in January he was named foreign minister, making his contacts more formal. The two countries have worked closely in recent months.
When Trump threatened to junk the North American Free Trade Agreement, as he had vowed on the campaign trail, Kushner and Videgaray hastily arranged for Peña Nieto to call him. Canada's prime minister, Justin Trudeau, also telephoned, and Trump backed down.
Mexico still sometimes appears in Trump's crosshairs. On Thursday, he tweeted that Mexico "was just ranked the second deadliest country in the world, after only Syria."
He added: "We will BUILD THE WALL!" Mexican officials have said the report Trump cited, issued by the International Institute for Strategic Studies, a British think tank, was misleading.
Israel's prime minister, Benjamin Netanyahu, also turned to Kushner, who he had known for years. Their personal ties have helped propel the president's son-in-law into the unlikely position of Middle East peace negotiator.
The two met this week in Jerusalem, a follow-up to Trump's visit to the region last month.
In Saudi Arabia, King Salman abruptly picked Mohammed bin Salman as heir to the throne this week, leapfrogging over the current crown prince in a twist to the kingdom's dynastic politics that may be tied to Kushner's role.
The two, both in their 30s, forged a friendship after the 2016 election, sharing dinners and exchanging phone calls. They played a key role in setting up Trump's successful visit to Riyadh last month, where the royal family treated the Trumps like royalty and Trump offered gushing praise for the autocratic regime.
By then, the media had dubbed Kushner and MBS, as he is widely known, the "two princes."
"MBS quickly latched on to Jared Kushner as a channel to the White House," said F. Gregory Gause, head of the international affairs department at Texas A&M University and long-time observer of Saudi politics.
Trump is hardly the first president to run major parts of his foreign policy from the White House.
President Obama's aides conducted the secret diplomacy that led to restoration of diplomatic ties with Cuba in 2015, bypassing the State Department. And at least in his first term, he picked special envoys to conduct policy for the Middle East and relations with Afghanistan and Pakistan.
But in Obama's second term, Secretary of State John F. Kerry helped lead the negotiations that led to the 2015 landmark accord to curb Iran's nuclear weapons capability, arguably Obama's most significant achievement in foreign affairs.
Trump meets frequently with Secretary of State Rex Tillerson and seems to value his counsel. But Trump overrode Tillerson's concerns when he announced plans to withdraw from the Paris climate accord aimed at reducing global warming.
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