(Reuters) - A witness testified at Wednesday’s first public impeachment hearing that President Donald Trump seemed to care more about his own political interests than about Ukraine’s welfare as the U.S. leader assessed ties with that country.

Bill Taylor, the top U.S. diplomat in Ukraine, disclosed that a member of his staff overheard a July 26 phone call in which Trump asked Gordon Sondland, the U.S. ambassador to the European Union, about “the investigations.”

Sondland responded that the Ukrainians were “ready to move forward,” Taylor told the congressional committee hearing.

Taylor’s staff member was in Kiev with Sondland when the phone call took place, Taylor said. Earlier that day, Sondland and Taylor’s staff member had met a top adviser to Ukrainian president Volodymyr Zelenskiy.

The day before Trump spoke from the White House with Zelenskiy by phone and pressed the Ukrainian leader to investigate a political rival, Democratic presidential front-runner Joe Biden, and Biden’s son Hunter.

Asked about the incident by U.S. House Intelligence Committee Chairman Adam Schiff on Wednesday, Taylor said Sondland told the staffer Trump was most focused on probes into Biden, the former vice president, and Hunter Biden.

“I take it that the import of that is he (Trump) cares more about that (the investigations) than he does about Ukraine?” Schiff asked.

“Yes, sir,” Taylor replied.

Taylor said he was more alarmed by a hold Trump had placed on security assistance to Ukraine than the dangling of a possible Trump-Zelenskiy White House meeting:

“It’s one thing to try to leverage a meeting in the White House,” Taylor said.

“It’s another thing, I thought, to leverage security assistance – security assistance to a country at war, dependent on both the security assistance and the demonstration of support. It was much more alarming,” he added.

The focus of the inquiry has been on Trump’s July 25 call urging Zelenskiy to open a corruption investigation into the Bidens and a discredited theory that Ukraine, not Russia, meddled in the 2016 U.S. election.

Hunter Biden had worked for a Ukrainian energy company called Burisma.

Democrats are also looking into whether Trump abused his power by withholding $391 million in security aid to Ukraine - a vulnerable U.S. ally facing Russian aggression - as leverage to pressure Kiev into conducting investigations politically beneficial to Trump.

The money - approved by the U.S. Congress to help Ukraine combat Russia-backed separatists in the eastern part of the country - was later provided to Ukraine.