Documents released by the White House budget office on Tuesday show that officials prepared to freeze military aid to Ukraine the day before President Donald Trump's July 25 phone call with Ukrainian President Volodymyr Zelensky.

The documents show White House budget officials sharing a "Ukraine prep memo" the day before Trump talked to Ukraine's president and urged him to probe former Vice President Joe Biden and his son over bogus allegations of corruption.

Most details from the Ukraine memo are heavily redacted, as well as many parts of other emails that part of the document release.

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Officials at the White House budget office prepared to freeze almost $400 million in military aid to Ukraine the day before President Donald Trump's July 25 phone call with President Volodymyr Zelensky of Ukraine, new documents show.

The revelation came on the same day as opening arguments began in Trump's Senate impeachment trial, The documents were released in response to an FOIA request by the transparency group American Oversight.

In one email, dated July 24 — the day before Trump's July 25 phonecall with Zelensky — budget officials shared a "Ukraine Prep Memo" with Michael Duffey, the budget official who played a key role in the Ukraine aid freeze.

The messages, like most of the emails released Tuesday, are heavily redacted.

"We will be standing by to answer any questions that you have and are happy to schedule time to discuss if you like," OMB official Paul Denaro wrote to Duffey.

The day after, Duffey asked budget official Mark Sandy about the footnote, which is the techincal device used to freeze the funding.

In response, Sandy shared what he called a "revised footnote."

A White House summary of Trump's July 25 phone call with Zelensky shows him repeatedly pressuring Zelensky to pursue investigations that would be politically beneficial to the president. The first was a probe of Burisma Holdings, a Ukrainian natural-gas company whose board employed Hunter Biden, the son of former Vice President Joe Biden, until last year.

The elder Biden is currently vying for the 2020 Democratic presidential nomination and is a frontrunner in the race.

The second investigation asked Zelensky to launch focused on a bogus conspiracy theory suggesting Ukraine interfered in the 2016 election to help Democrats.

The phone call took place one day after the former special counsel Robert Mueller testified to Congress that the Russian government interfered in the 2016 race in a sweeping, systematic fashion to help the Trump campaign.

Trump's campaign, in turn, welcomed the interference and sought to benefit from it, Mueller found.

Roughly 90 minutes after Trump's phone call with Zelensky, Duffey officially froze Ukraine's military aid.

Later emails show Pentagon official Elaine McCusker raising concerns about the legality of the freeze, but these sections are also heavily redacted.

In an email previously obtained by the national-security blog Just Security, McCusker replied "You can't be serious. I'm speechless," when budget officials tried to shift the responsibility for the budget freeze to the Pentagon.

In later exchanges, officials questioned what had happened to the frozen aid.

Last week, the nonpartisan Government Accountability Office found that the OMB violated the Impoundment Control Act, a law that limits when a president can defer congressionally approved spending, by substituting "his own policy priorities for those that Congress has enacted into law."

"The public can now see even more evidence of the President's corrupt scheme as it unfolded in real-time," Austin Evers, executive director of American Oversight, said in a statement Wednesday morning. "The volume of material released, and the volume of material still secreted away only highlights how much the administration has withheld from the House, the Senate, and the American public."