The revelation in a written book manuscript of John Bolton, a former top aide of Donald Trump, undercuts Trump's versions of events in the Ukraine affair.
With this, senate Republicans thus far have refused to allow any witnesses or new evidence in the trial may force to vote to call for Bolton to testify in the trial. Republican Senator Mitt Romney, a sometime critic of Trump, said there was a growing likelihood that at least four Republican senators would vote to call for Bolton to testify in the trial, which would give Democrats the votes necessary to summon the former national security adviser.
Senate Republicans thus far have refused to allow any witnesses or new evidence in the trial that will determine whether Trump is removed from office. The president's legal team is set to resume its defense of Trump on Monday afternoon.
The New York Times cited the manuscript of an unpublished book by Bolton as saying that Trump told him he wanted to freeze security aid to Ukraine until Kiev helped with politically beneficial investigations into Democrats, including former Vice President Joe Biden and his son, Hunter Biden.
If confirmed, the report would add weight to Democrats' accusations that Trump used the $391 million in aid - approved by the U.S. Congress to help Ukraine combat Russia-backed separatists - as leverage to get a foreign country to help him dig up dirt on a domestic political rival.
Biden is a leading contender for the Democratic nomination to face Trump in the Nov. 3 presidential election. Trump on Monday denied telling Bolton that he sought to use the aid to pressure Ukrainian President Volodomyr Zelenskiy to investigate the Bidens on unsubstantiated corruption allegations. Hunter Biden worked for a Ukrainian energy firm while his father was U.S. vice president.
Bolton left his post in September. Trump said he fired him. Bolton said he quit. "I think it's increasingly likely that other Republicans will join those of us who think we should hear from John Bolton," Romney told reporters. Romney, the 2012 Republican presidential nominee, added that "Bolton's relevance ... is becoming increasingly clear."
Another moderate Republican senator, Susan Collins, said the reports regarding Bolton's book "strengthen the case for witnesses and have prompted a number of conversations among my colleagues."
The Democratic-led House of Representatives impeached Trump last month on charges of abuse of power in his dealings with Ukraine and obstruction of Congress, setting up the trial in the Republican-led Senate.
Trump is expected to be acquitted in the 100-seat Senate, where Republicans hold 53 seats and a two-thirds vote is required to convict and remove a president from office. No Republican senator has voiced support for his ouster.
Trump denied telling Bolton he was seeking something in return for unfreezing the Ukrainian aid, which eventually was provided in September after the controversy became public. "I NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats, including the Bidens ... If John Bolton said this, it was only to sell a book," Trump wrote on Twitter.