US President Donald Trump's acting chief of staff on Thursday acknowledged that Mr Trump held up $391 million in military aid to Ukraine in part to make the money contingent upon the Ukrainians investigating a US domestic political matter involving the Democratic Party.
Mr Trump and administration officials had denied for weeks that it had demanded a "quid pro quo" - a Latin phrase meaning favour for favour - for delivering the US aid, a key part of a controversy that has triggered an impeachment inquiry in the House of Representatives against the Republican president.
But acting White House chief of staff Mick Mulvaney acknowledged in a briefing with reporters that the US aid was held up over Mr Trump's concerns about a Democratic National Committee (DNC) computer server alleged to be in Ukraine.
In a 25 July call, Mr Trump asked Ukrainian President Volodymyr Zelenskiy for "a favour" to look into the server and another matter relating to the 2016 election.
Mr Trump also asked Mr Zelenskiy to investigate a domestic political opponent, Joe Biden, and Mr Biden's son Hunter Biden, who had served as a director for Ukrainian energy company Burisma.
Mr Zelenskiy agreed during the call to carry out the investigation Mr Trump sought. The US aid later was provided to Ukraine.
The DNC server issue is a debunked conspiracy theory that Ukraine and not Russia interfered in the 2016 US election and that a Democratic Party computer server was being held somewhere in Ukraine.
Mr Mulvaney said Mr Trump did not like foreign aid, thought Ukraine was corrupt, and was annoyed at how little "lethal aid" European nations provided to Ukraine as it combated Russia-backed separatists in the eastern part of the country.
"Did he also mention to me in the past, the corruption related to the DNC server? Absolutely. No question," Mr Mulvaney said, referring to Mr Trump. "But that's it. That's why we held up the money."
"The look-back to what happened in 2016 certainly was part of the things that he was worried about in corruption in that nation," Mr Mulvaney said, referring to Mr Trump.
A reporter told Mr Mulvaney that what he just described was a quid pro quo. "We do that all the time with foreign policy," Mr Mulvaney responded.