President Donald Trump's impeachment trial in the Senate is almost sure to end within two weeks, a senior administration official said on Wednesday.

The official, speaking on condition of anonymity, said, "I think it's extraordinarily unlikely it will be going beyond two weeks."

According to the official, the White House believes it has an easy case and the Republican-controlled Senate will quickly acquit. Mr Trump is accused of abusing his office and obstructing Congress.

"The Senate's not going to have any need" to go longer, the official said. "The president should be acquitted. We think it's going to happen and going to happen readily."

The US House of Representatives voted earlier to send the two articles to the Senate, which will open its trial on Tuesday. The drama interrupts an already busy political calendar, with Mr Trump scheduled to give his annual State of the Union address before Congress two weeks later on February 4.

The Democrats announced a seven-person team to present the case against Mr Trump in the Senate, but the White House has yet to unveil its defence panel.

That will come "soon," the administration official said.

The Trump representative would not even rule out the entire case being discarded, saying the evidence was so weak that "if this were a court proceeding, this would be a case for dismissal."

The official said that "would be an appropriate thing to do."

Democrats have been repeatedly frustrated in their attempts to call witnesses or obtain evidence from the Trump administration during the House investigation. They are now pushing for the Senate to call some of those officials and ex-officials to the witness stand in the trial.

But the official said it was very unlikely that Mr Trump would relent and allow one of the highest profile potential witnesses, fired national security advisor John Bolton, to testify.

"It would be extraordinary to have the national security advisor to testify," the official said.

"We don't think there's going to be any need for witnesses... because this is an extraordinary weak case."

However, if the trial doesn't take its predicted quick course and the Democrats succeed in forcing the appearance of witnesses, then the White House "is going to have a right" to call its own witnesses, the official said.

The defence presentation at the opening of the trial will be brief, he promised.

"The reason is it doesn't take a very long time is the facts are simple," the official said, claiming that the Democrats "don't have any evidence." (AFP)

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