US President Donald Trump's lawyers will wrap up their arguments on Tuesday in the Senate impeachment trial after spending Monday making arguments attacking Trump's political rival, former Vice President Joe Biden. Watch the Senate proceedings streaming live here at 1 p.m. ET.

In about seven hours of arguments before the Senate on Monday, Trump's lawyers also largely ignored revelations in an unpublished manuscript by John Bolton, Trump's former national security adviser, that go to the heart of impeachment charges against Trump.

Trump's lawyers said they would continue their presentations on Tuesday. It was not clear when senators would begin submitting their questions to US Chief Justice John Roberts, the next step in the Senate impeachment trial.

Lawyer Pat Cipollone concluded Monday's session with Republicans' argument that Democrats were using impeachment as a way to overturn the results of the 2016 election as the next presidential vote approaches.

"An election is only months away and for the first time in history they are asking you to remove a president from the ballot,” he said.

Bolton wrote that Trump told him he wanted to freeze $391 million in security aid to Ukraine until Kyiv helped with investigations into Democrats including Democratic political rival Joe Biden, and his son Hunter Biden.

The Bolton disclosures prompted new calls by Democrats for Bolton and other witnesses to testify. Trump is accused of abusing the power of his office in seeking foreign interference in a US election and of obstructing Congress.

Some moderate Republicans, including Senators Mitt Romney and Susan Collins, said the disclosures were likely to sway at least four Republicans to call Bolton to testify, which would give Democrats the votes necessary in the Republican-led Senate to summon him.

Senate Republicans have so far refused, however, to allow any witnesses or new evidence in the trial that will determine whether Trump is removed from office.

Trump denied telling Bolton he sought to use the Ukraine aid as leverage to get Kyiv to investigate the Bidens.

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.

As Trump's legal team on Monday resumed its presentation of opening arguments in the trial, Bolton's name only surfaced in passing during the final presentation.

Instead, defense lawyers turned to Biden, one of Trump's leading Democratic rivals as he seeks re-election in November, and his son Hunter, who sat on the board of Ukrainian energy company Burisma while his father was US vice president.

Attorney Pam Bondi defended Trump's use of unsupported corruption allegations against the Bidens as the basis for his demand that Ukraine investigate them. That drew a rebuke from Biden campaign spokesman Andrew Bates, who dismissed Bondi's allegations as having been widely discredited.

Ukrainian officials have said they found no indication that Hunter Biden had broken any law.

The Senate may resolve the issue of whether to call witnesses in a vote on Friday or Saturday.

By David Morgan and Patricia Zengerle/Reuters

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