WASHINGTON — Kurt D. Volker, the State Department’s special envoy for Ukraine who got caught in the middle of the pressure campaign by President Donald Trump and his lawyer, Rudy Giuliani, to find damaging information about Democrats, abruptly resigned his post today.

Volker, who told Secretary of State Mike Pompeo today that he was stepping down, offered no public explanation, but a person informed about his decision said he concluded that it was impossible to be effective in his assignment given the developments of recent days.

His departure was the first resignation since revelations about Trump’s efforts to pressure Ukraine’s president to investigate former Vice President Joe Biden and other Democrats. The disclosures have triggered a full-blown House impeachment inquiry, and House leaders announced today that they planned to interview Volker in a deposition next week.

Volker, a former ambassador to NATO who served in the part-time, unpaid position to help Ukraine resolve its armed confrontation with Russian-sponsored separatists, was among the government officials who found themselves in an awkward position because of the search for dirt on Democrats, reluctant to cross the president or Giuliani, yet wary of getting drawn into politics outside their purview.

The unidentified intelligence official who filed the whistleblower complaint that brought the president’s actions to light identified Volker as one of the officials trying to “contain the damage” by advising Ukrainians how to navigate Giuliani’s campaign.

Volker facilitated an entree for Giuliani with the newly elected government in Ukraine, acting not at the instruction of Trump or Pompeo but at the request of the Ukrainians who were worried that Giuliani was making the rounds seeking information about Biden and other Democrats.

The Ukrainians were concerned about the impact of their relationship with the United States, their most important patron against Russia. Andriy Yermak, a close aide to President Volodymyr Zelenskiy, asked Volker in July to connect him with Giuliani so the Ukrainian government could hear out his issues. Volker agreed to reach out to the former New York mayor to see if he would sit down with the Ukrainian official.

Volker then contacted Giuliani to ask if he would want to speak with Yermak, and the mayor agreed. Volker and Giuliani had breakfast to discuss Ukraine.

“Mr. Mayor — really enjoyed breakfast this morning,” Volker wrote in a text later that day that Giuliani posted on Twitter this week. Volker set up a conference call between Giuliani and Yermak, who then later also met in person in Madrid on Aug. 2.

Giuliani has seized on Volker’s call to him to assert that he was acting at the behest of the State Department. He said he spoke with Volker eight times and displayed the text messages on Laura Ingraham’s show on Fox News on Thursday night, calling on Volker to confirm that the department initiated contact.

“He should step forward and explain what he did,” Giuliani said on the show. “The whistleblower falsely alleges that I was operating on my own. Well, I wasn’t operating on my own!”

Referring to Volker and Gordon Sandland, the ambassador to the European Union, Giuliani added: “They basically knew everything I was doing. So, it was being done with the authorization and at the request — and then I have a final one in which they — there is a big ‘thank you’ about how my honest and straightforward discussion led to solving a problem in the relationship.”

The State Department did not respond to a request for comment on Volker’s resignation nor did it leap to his defense after The New York Times first reported on his role in facilitating Giuliani’s talks with the new Ukrainian government.

In a statement last month in response to that story, a department spokesperson said that Volker “has confirmed that, at Presidential Advisor Andriy Yermak’s request, Volker put Yermak in direct contact with Mr. Giuliani.” The statement went on to stress that Giuliani “is a private citizen and acts in a personal capacity as a lawyer for President Trump. He does not speak on behalf of the U.S. Government.”

Just days after Giuliani’s breakfast with Volker and the follow-up phone call with Yermak, Trump spoke on the telephone with Zelenskiy. After the Ukrainian president described his need for more U.S. assistance against Russia, Trump asked him “to do us a favor, though,” and look into Democrats.

Volker was not on that call and was neither shown a copy of the rough transcript reconstructed from the conversation nor told that the president raised Biden, according to one person informed about the series of events. Volker participated in Trump’s meeting with Zelenskiy on the sideline of the United Nations this week in his last official duty.

Volker, a former career foreign service officer who represented President George W. Bush at NATO and now serves as executive director of the McCain Institute for International Leadership at Arizona State University based in Washington, spent much of the year trying to bring Trump together with Zelenskiy to bolster the government elected earlier this year.

He argued to Trump administration officials that Zelenskiy was a credible reformer and serious figure who could be his country’s last chance to get its act together in the face of Russian aggression. With Trump openly expressing his disdain for Ukrainians, convinced that they were all corrupt and tried to take him down in 2016, it was an uphill task.

After the Ukrainian inauguration, Trump agreed to meet with Zelenskiy, but his staff kept delaying putting a date on the calendar. Like other officials, Volker was surprised to learn that Trump had ordered $391 million in aid to Ukraine frozen.

But he kept working to bring the two presidents together. Finally, the White House agreed to schedule a meeting between Trump and Zelenskiy during a visit by the American president to Warsaw, Poland, only to scratch the meeting when Trump decided to stay home to monitor a hurricane.

Instead, Vice President Mike Pence, whose trip to Zelenskiy’s inauguration was canceled to increase leverage on the Ukrainian government, according to the whistleblower complaint, was sent to meet with Zelenskiy in Warsaw in his place.

Volker’s departure, which was first reported by the State Press, the student newspaper at Arizona State University, leaves the Trump administration with few senior officials versed in Ukraine’s struggles with Russia.

In recent months, the administration has lost John Bolton, the national security adviser; Fiona Hill, the top Europe official on the National Security Council staff; and Dan Coats, the director of national intelligence, all of whom sympathized with Ukraine in its struggle with Russia.

Moreover, the U.S. Embassy in Kyiv is still without an ambassador after the administration yanked home Ambassador Marie Yovanovitch, a career diplomat who was targeted by the president and Giuliani for allegedly being insufficiently loyal, a charge heatedly disputed by her colleagues.

© 2019 The New York Times Company