But Mr. Sondland donated $1 million through his companies to the inaugural committee for Mr. Trump, who subsequently tapped Mr. Sondland last year to be United States ambassador to the European Union.
The role traditionally has not focused on Ukraine, which is not part of the European Union, but Mr. Sondland increasingly worked to establish himself as a central figure in Ukraine policy, administration officials said.
Mr. Sondland came to be seen in the administration as more loyal to Mr. Trump than was Mr. Volker, an acolyte of the late Senator John McCain, an outspoken critic of the president.
Mr. Sondland told reporters last month that he saw Ukraine as among a handful of “low-hanging fruit” policy areas where the European Union could work together with Washington to improve relations.
Mr. Sondland raised some hackles at the State Department and in the National Security Council when he asked to be included in the United States delegation that attended Mr. Zelensky’s inauguration, according to people familiar with the events. They said Mr. Sondland pushed for an Oval Office meeting afterward for the delegation — which also included Mr. Volker, Energy Secretary Rick Perry and Senator Ron Johnson, Republican of Wisconsin — to brief Mr. Trump on the delegation’s impressions of Mr. Zelensky.
When the delegation praised Mr. Zelensky and urged Mr. Trump to fully support the new Ukrainian government, the president was dismissive. “They’re terrible people,” Mr. Trump said of Ukrainian politicians, according to people familiar with the meeting. “They’re all corrupt and they tried to take me down.”
Mr. Sondland continued building a relationship with Mr. Zelensky, inviting him to a June dinner at the United States mission to the European Union in Brussels, and meeting him again in Kiev in July with Mr. Volker on the day after Mr. Trump’s phone call with Mr. Zelensky.
And Mr. Sondland kept in contact with Mr. Zelensky’s aides, who have told people that Mr. Sondland urged them to encourage the Ukrainian president to push forward with investigations into Burisma and the 2016 election.