A newly-released government email has revealed that the White House sought to freeze aid to Ukraine just 91 minutes after President Donald Trump spoke to President Volodymyr Zelensky by phone in July.

The email, telling the Pentagon to “hold off”, was sent by a senior White House official.

In the phone call, President Trump asked the Ukrainian leader to investigate his political rival, Democrat Joe Biden.

On December 18, President Trump has been impeached for abuse of power over the issue.

Democrats say the phone call shows Donald Trump used the office for personal political gain.

A US whistleblower who heard about the conversation raised concerns, which ultimately triggered the impeachment inquiry.

The president was formally impeached by the Democratic-controlled House of Representatives, but is unlikely to be removed from office as the case will go to trial in the Senate, where his Republican party has a majority.

The newly-released email was obtained by the Center for Public Integrity following a court order in a freedom of information case.

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The email shows that Mike Duffey, a senior White House official, contacted senior defense officials about withholding Ukraine’s aid just over an hour-and-a-half after President Trump ended a call with President Zelensky on July 25.

The White House declassified the Ukraine call transcript following a whistleblower complaint it was being covered-up.

The transcript shows President Trump asked Volodymyr Zelensky to “do us a favor” and investigate Joe Biden, currently a frontrunner to be the Democratic candidate in the 2020 White House race, and his son Hunter Biden, who had previously worked for a Ukrainian energy company.

In the email Mike Duffey asks that the Department of Defense “hold off” on providing aid following the administration’s plan to review.

The email reads: “Given the sensitive nature of the request, I appreciate your keeping that information closely held to those who need to know to execute direction.”

In a statement released to media on December 22, Rachel Semmel, a spokeswoman for the Office of Management and Budget, dismissed the characterization of the email.