The White House on Sunday signaled comfort with plans by Senate Republicans to avoid new witnesses in U.S. President Donald Trump's impeachment trial, while a top Democrat seized on a newly released email on the withholding of U.S. aid to Ukraine to press his case for testimony.

The Democratic-led House of Representatives approved two impeachment charges against Trump on Wednesday over his pressuring of Ukraine to investigate a political rival. There is little chance he will be convicted and removed from office through a trial in a Senate controlled by fellow Republicans, Globalnews reports.

Democrats are pushing to call top Trump aides to testify, but Senate Majority Leader Mitch McConnell wants the Senate to consider the case without hearing from new witnesses.

The Senate's top Democrat, Chuck Schumer, told reporters in New York that an email made public on Saturday about military assistance to Kyiv underscored the need for witnesses.

The email, obtained by the Center for Public Integrity through a court order in a Freedom of Information Act case, showed senior White House budget official Michael Duffey directing the Pentagon to withhold the aid just 91 minutes after Trump concluded a July 25 phone call with Ukrainian President Volodymyr Zelensky.

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In testimony to Congress last month, however, U.S. Ambassador to the European Union Gordon Sondland said he was first informed on July 18 that the White House was withholding security aid to Ukraine. "I was never able to obtain a clear answer regarding the specific reason for the hold," he added.

The aid and the Trump-Zelensky call are at the heart of the impeachment case put together by Democrats, and Duffey is one of the four witnesses Schumer has proposed calling.

"If there was ever an argument that we need Mr. Duffey to come and testify, this is that information," Schumer said.

While Trump had indicated an interest in calling separate witnesses in his defense, he has also said he would go along with whatever decision McConnell and other Senate Republican leaders make.

In remarks on Sunday talk shows, Marc Short, chief of staff to Vice President Mike Pence, indicated the White House was on board with McConnell's goal of a speedy trial.

"The American people are tired of this sham," Short said on NBC's "Meet the Press."

"To the extent that there’s a prolonged trial, we’re not anxious about that," he said. "Our administration is anxious to get back to working for the American people … We've had a lot of witnesses already."

Lawmakers left Washington for a holiday break on Friday at loggerheads over how to proceed.