Waiters were coming and going as U.S. Ambassador to the European Union Gordon Sondland spoke on the phone with President Trump on July 26 from the outdoor section of a central Kyiv restaurant and discussed the Ukrainian president’s willingness to conduct politically charged investigations, an episode that also highlighted the lack of security around a presidential call, according to testimony to Congress and a person familiar with the episode.

Sondland arrived in Kyiv and scrapped a schedule the embassy had arranged for him, which included a meeting with the man who would subsequently become Ukraine’s prime minister, instead saying he wanted to meet only with Volodymr Zelensky, the Ukrainian president, and the two aides closest to him: head of the presidential administration Andriy Bohdan and adviser Andriy Yermak, according to the person, who spoke on the condition of anonymity given the sensitive nature of the subject.

Sondland’s interactions in Kyiv — the day after Trump called Zelensky and exhorted him to investigate former vice president Joe Biden — will be scrutinized in public testimony Sondland is scheduled to give this week at the impeachment inquiry.

Robert Luskin, an attorney for Sondland, didn’t respond to a request for comment.

Congressional focus has intensified on the episode at the Kyiv restaurant called SHO, in which Sondland pulled out his mobile phone and dialed up Trump. In a closed-door hearing on Friday, David Holmes, an embassy staffer who was sitting at the table, testified that he overheard the conversation, which began with Trump asking if Sondland was calling from Ukraine.

“Ambassador Sondland replied, yes, he was in Ukraine, and went on to state that President Zelensky ‘loves your ass,’ ” Holmes testified in his opening statement. “I then heard President Trump ask, ‘So, he’s gonna do the investigation?’ Ambassador Sondland replied that ‘he’s gonna do it,’ adding that President Zelensky will do ‘anything you ask him to.’ ”

Two other people were sitting at the table at the time and would potentially be able to corroborate Holmes’s account: Suriya Jayanti, an embassy staffer who served as Sondland’s control officer for the trip, meaning she arranged his schedule and accompanied him wherever he went, and Tara Maher, a political officer at the U.S. Embassy in Brussels, according to people with knowledge of the lunch.

Sondland didn’t receive the kind of direct assurances he relayed to Trump during the meetings he held earlier that day with Zelensky and Bohdan, according to testimony from Holmes and people familiar with those meetings.

But Sondland did slip away for a one-on-one meeting with Yermak after meeting Zelensky, and shortly after that meeting concluded, went to the Kyiv restaurant and placed the phone call to Trump. Holmes testified that he was blocked from attending the meeting with Yermak as a note taker.

Sondland was also texting back and forth on WhatsApp with Yermak throughout the trip, and had been communicating with other Ukrainian officials over the messaging app in the preceding and subsequent months, according to people familiar with his interactions.

Most of those messages haven’t been made public or handed over to the House impeachment inquiry. The messages by Sondland that have been released are those in which he was communicating in a three-way conversation with Yermak and former Ukraine special envoy Kurt Volker. Volker, who stepped down from the post after a whistleblower complaint from a CIA analyst triggered the impeachment probe, turned those communications over to the committees leading the inquiry.

The chairmen of the House Foreign Affairs, Intelligence and Oversight committees subpoenaed communications and documents from Sondland as the inquiry got underway, and Sondland turned over communications from his personal devices to the State Department. But according to a statement by the committee chairmen in October, the State Department withheld them from the impeachment inquiry, defying a subpoena the committees issued to Secretary of State Mike Pompeo.

Sondland, a wealthy Republican hotelier from the Pacific Northwest who became Trump’s ambassador to the European Union after donating $1 million to the president’s inauguration committee, handled a number of situations for Trump that would normally be considered outside the remit of his position in Brussels. He swooped in to take over the Ukraine portfolio after Trump’s personal attorney, Rudolph W. Giuliani, helped engineer the ouster of U.S. Ambassador to Ukraine Marie Yovanovitch.

During the course of the phone call from the restaurant, Sondland also consulted with Trump on another matter of importance to the president at the time: efforts to free the American rapper A$AP Rocky from jail in Sweden at the request of reality television star Kim Kardashian.

The same day as his July 25 phone call with Zelensky, Trump lashed out at Sweden on Twitter and demanded the nation free the American rapper despite his assault charge from his role in a street brawl.

“Give A$AP Rocky his FREEDOM,” Trump tweeted. “We do so much for Sweden but it doesn’t seem to work the other way around. Sweden should focus on its real crime problem!”

Sondland, according to Holmes’s opening statement, advised Trump to “let him get sentenced, play the racism card, give him a ticker-tape when he comes home.” Sondland added that Sweden should have released the rapper on Trump’s word, but the president could at least tell the Kardashians he tried, according to Holmes’s recollection.

According to a senior White House aide, who, like others, spoke on the condition of anonymity to discuss a diplomatic issue, Sondland was involved in the A$AP Rocky effort because of his relationship with Jared Kushner and Ivanka Trump, and because Trump saw him as “the Europe guy.”

Apart from sending national security adviser Robert O’Brien, who was then his top hostage negotiator, to intervene in the matter, Trump pressured Sweden’s leader on a phone call to release the rapper, saying that the United States does a lot for Sweden and Sweden should do this for him, according to a U.S. official.

Swedish officials tried to explain they needed to let the courts deal with the matter, but Trump was angered, saying it should have been easy for the Swedish government to do as he asked, the official said. Swedish officials were baffled by Trump’s aggressive involvement in the case, the official added.

In early August, Sweden released A$AP Rocky from jail after he was detained for a month on assault charges. According to the official familiar with the episode, Trump was frustrated that he didn’t get enough credit for securing the rapper’s release.

This report has been updated to reflect the correct designation for Tara Maher, who is a political officer at the U.S. Embassy in Brussels.

Aaron C. Davis contributed to this report.