Washington (CNN) Lead House impeachment manager Rep. Adam Schiff argued Monday that Republican senators cannot say they want "a search for the truth" in President Donald Trump's impeachment trial if they don't vote to subpoena former national security adviser John Bolton.

On Sunday, The New York Times, citing multiple people's descriptions of an unpublished draft manuscript by Bolton, reported Trump in August told his then-national security adviser that he wanted to continue holding military aid to Ukraine until the country helped with investigations into Democrats, including former Vice President Joe Biden. Trump's purported statement, as described by Bolton, would directly tie the US military aid freeze with the President's requests that Ukraine announce investigations into his political rivals -- undermining a key pillar of the President's impeachment defense that the two circumstances are unrelated.

The news has placed new pressure on Senate Republicans to allow witnesses , including Bolton, to testify in the trial.

"I think for the senators, and I'm just not talking about the four that been so much the focus of attention, for every senator, Democrat and Republican, I don't know how you can explain that you wanted a search for the truth in this trial and say you don't want to hear from a witness who had a direct conversation about the central allegation in the articles of impeachment," Schiff told CNN's Alisyn Camerota on "New Day" Monday.

The new revelations change the Senate trial "very dramatically," said Schiff, the House Intelligence Committee chairman.

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