WASHINGTON — Kurt D. Volker, the State Department’s special envoy for Ukraine who got caught in the middle of the pressure campaign by President Trump and his lawyer, Rudolph W. Giuliani, to find damaging information about Democrats, abruptly resigned his post on Friday.
Mr. Volker, who told Secretary of State Mike Pompeo on Friday 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 Mr. Trump’s efforts to pressure Ukraine’s president to investigate former Vice President Joseph R. Biden Jr. and other Democrats. The disclosures have triggered a full-blown House impeachment inquiry, and House leaders announced on Friday that they planned to interview Mr. Volker in a deposition on Thursday.
Mr. Volker, a widely respected former ambassador to NATO, served in the part-time, unpaid position of special envoy to help Ukraine resolve its armed confrontation with Russia-sponsored separatists. He 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 Mr. Giuliani yet wary of getting drawn into politics outside their purview.
The unidentified intelligence official who filed the whistle-blower complaint that brought the president’s actions to light identified Mr. Volker as one of the officials trying to “contain the damage” by advising Ukrainians how to navigate Mr. Giuliani’s campaign.
Mr. Volker facilitated an entree for Mr. Giuliani with the newly elected government in Ukraine, acting not at the instruction of Mr. Trump or Mr. Pompeo, but at the request of the Ukrainians, who were worried because Mr. Giuliani was seeking information about Mr. Biden and other Democrats and had denounced top Ukrainian officials as “enemies of the president.”
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 Zelensky, asked Mr. Volker in July to connect him with Mr. Giuliani, a former mayor of New York, so the Ukrainian government could hear out his issues. Mr. Volker agreed to reach out to the former mayor to see if he would sit down with the Ukrainian official.
Mr. Volker then contacted Mr. Giuliani to ask if he would want to speak with Mr. Yermak, and the mayor agreed. Mr. Volker and Mr. Giuliani had breakfast to discuss Ukraine.
“Mr. Mayor — really enjoyed breakfast this morning,” Mr. Volker wrote in a text later that day that Mr. Giuliani posted this week on Twitter. Mr. Volker set up a conference call between Mr. Giuliani and Mr. Yermak, who then later met in person in Madrid, on Aug. 2.
Mr. Giuliani has seized on Mr. Volker’s call to him to assert that he was acting at the behest of the State Department. He said he spoke with Mr. Volker eight times and displayed the texts on Thursday night on Laura Ingraham’s show on Fox News, calling on Mr. Volker to confirm that the department initiated contact.
“He should step forward and explain what he did,” Mr. Giuliani said on the show. “The whistle-blower falsely alleges that I was operating on my own. Well, I wasn’t operating on my own!”
Referring to Mr. Volker and Gordon Sondland, the ambassador to the European Union, Mr. 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.”
Reacting to Mr. Volker’s resignation on Friday night, Mr. Giuliani said his release of the texts was not intended to get him “in trouble,” and he defended the special envoy’s role in facilitating the talks with Mr. Yermak.
“I was in the unique position to help them,” Mr. Giuliani said of the State Department, adding that he kept both Mr. Volker and Mr. Sondland apprised of the talks.
The State Department did not respond to a request for comment on Mr. Volker’s resignation on Friday, nor did it leap to his defense after The New York Times first reported on his role in facilitating Mr. Giuliani’s talks with the new Ukrainian government.
In response to that article, the department said in a statement last month that Mr. 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 Mr. 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 Mr. Giuliani’s breakfast with Mr. Volker and the follow-up phone call with Mr. Yermak, Mr. Trump spoke on the telephone with Mr. Zelensky. After the Ukrainian president described his need for more American assistance against Russia, Mr. Trump asked him to “do us a favor, though” and look into Democrats.
Mr. Volker was not on that call, and he was neither shown a copy of the transcript reconstructed from the conversation nor told that the president mentioned Mr. Biden, according to one person informed about the series of events. Mr. Volker participated in Mr. Trump’s meeting with Mr. Zelensky on the sidelines of the United Nations General Assembly session this week in his last official duty.
“Kurt was one of the good ones who went in to the administration to stave off disaster,” said Thomas Wright, a senior fellow at the Brookings Institution. “They all have to speak out now about everything they know and let the chips fall where they may.”
Mr. Volker, a former career foreign service officer who represented President George W. Bush at NATO and now serves as the executive director of the McCain Institute for International Leadership at Arizona State University based in Washington, spent much of the year trying to bring Mr. Trump together with Mr. Zelensky to bolster the government elected in April.
He argued to Trump administration officials that Mr. Zelensky 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. It was an uphill task, given Mr. Trump’s open disdain for Ukrainians; “they’re all corrupt and they tried to take me down,” he said in a private meeting last spring.
After the Ukrainian inauguration, Mr. Trump agreed to meet with Mr. Zelensky, but his staff kept delaying putting a date on the calendar. Like other officials, Mr. Volker was surprised to learn that Mr. 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 Mr. Trump and Mr. Zelensky during the American president’s visit to Warsaw, only to scratch the meeting when Mr. Trump decided to stay home to monitor a hurricane.
Instead, Vice President Mike Pence, whose trip to Mr. Zelensky’s inauguration had been canceled to increase leverage on the Ukrainian government, according to the whistle-blower complaint, was sent to meet with Mr. Zelensky in Warsaw in his place.
Mr. 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 R. 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 conflict with Russia.
Moreover, the United States Embassy in Kiev is still without an ambassador after the administration yanked home Marie L. Yovanovitch, a career diplomat who was targeted by the president and Mr. Giuliani for ostensibly being insufficiently loyal, a charge heatedly disputed by her colleagues.
Senator Christopher S. Murphy, Democrat of Connecticut, expressed regret at Mr. Volker’s resignation. “He has a well deserved reputation for fairness, toughness and integrity, which is why I was so disappointed to see him caught up in this mess,” Mr. Murphy wrote on Twitter. “He now must put country first, and tell what he did and what he knows.”