US president Donald Trump’s legal team argued has forcefully against the relevance of testimony from John Bolton as they concluded their impeachment trial defence.

The Senate is braced for debate on whether to summon Mr Trump’s former national security adviser and other witnesses into the trial.

“This should end now, as quickly as possible,” White House counsel Pat Cipollone declared, capping a defence presentation that painted Mr Trump as a victim and took dismissive swipes at Mr Bolton, the potential witness who has scrambled Republican hopes for a swift end to the trial.

A day after the defence team largely brushed past Mr Bolton, lawyer Jay Sekulow addressed the controversy head-on by dismissing his manuscript — said to contradict a key defence argument about Mr Trump’s dealings with Ukraine — as “inadmissible”.

The argument was meant to dissuade Republicans from pursuing witnesses including Mr Bolton, who writes in a forthcoming book that Mr Trump told him he wanted to withhold military aid from Ukraine until it helped with investigations into Democratic rival Joe Biden.

“It is not a game of leaks and unsourced manuscripts,” Mr Sekulow said.

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White House counsel Pat Cipollone speaks during the impeachment trial (Senate Television via AP)

The argument built on a separate one on Monday night from Trump lawyer Alan Dershowitz, who said that nothing in the manuscript — even if true — rises to the level of an impeachable offence.

Mr Sekulow also sought to undermine the credibility of Mr Bolton’s book by noting that Attorney General William Barr has disputed comments attributed to him by Mr Bolton.

The legal team, in hours of arguments, delved into areas that Democrats see as outside the scope of impeachment, alleging law enforcement bias and seizing on surveillance errors the FBI has acknowledged making in its Russian election interference probe.

Mr Trump’s lawyers also argued that the Founding Fathers took care to make sure that impeachment was narrowly defined, with offences clearly enumerated.

“The bar for impeachment cannot be set this low,” Mr Sekulow said. “Danger. Danger. Danger. These articles must be rejected. The Constitution requires it. Justice demands it.”

The case now moves toward written questions, with senators on both sides getting 16 hours to pose queries. By late in the week, they are expected to hold a vote on whether or not to hear from any witnesses.

While scoffing at the manuscript, Mr Trump and the Republicans have strongly resisted summoning Mr Bolton to testify in person about what he saw and heard as Mr Trump’s top national security adviser.

Senate Republicans spent two days behind closed doors discussing ideas to satisfy those who want to hear more testimony without prolonging the proceedings – or jeopardising the president’s expected acquittal.

The ideas appear to be losing steam as quickly as they emerge.

One Republican, Senator James Lankford of Oklahoma, was floating an idea backed by Senator Lindsey Graham to subpoena Mr Bolton’s book manuscript so senators can see the evidence themselves — in private.

However, Chuck Schumer, the Senate’s top Democrat, called the proposal, which would keep Mr Bolton out of public testimony, “absurd”.

“We’re not bargaining with them. We want four witnesses, and four sets of documents, then the truth will come out,” Mr Schumer said.

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The president’s lawyers concluded their impeachment trial defence (Susan Walsh/AP)

Representative Adam Schiff, the chairman of the House intelligence committee and the lead Democratic prosecutor in the trial, added: “I don’t see how the oath of impartiality can be interpreted in any other way than demanding a fair trial that includes witnesses and documents.”

Other Republicans including Senator Pat Toomey want reciprocity – bring in Mr Bolton or another Democratic witness in exchange for one from the Republican side. Some Republicans want to hear from the Bidens.

Majority Leader Mitch McConnell gathered Republican senators again late on Tuesday to consider next steps.

The Republican leader is encouraging senators not to become tangled in such questions that could delay things. He wants a quick finish without new witnesses or testimony.

“One thing about Mitch McConnell – he does not panic,” said Senator Kevin Cramer.