Members of US congress are weighing up findings that President Donald Trump misused the power of his office for personal political gain and then obstructed an investigation as possible grounds for impeachment.

The US house judiciary committee is preparing for its first hearing since the release of a 300-page report by Democrats on the house intelligence committee that found "serious misconduct" by Mr Trump.

The report did not deliver a judgment on whether the US leader's actions stemming from a July 25 phone call with Ukraine's president rose to the constitutional level of "high crimes and misdemeanours" warranting impeachment - that will be for the full house to decide.

But its findings involving Mr Trump's efforts to seek foreign intervention in the American election process provide the basis for a house vote on impeachment and a senate trial carrying the penalty of removal from office.

Mr Trump has said he remains unconcerned about the unfolding inquiry in Washington.

While Democrats hold the majority in the US house of representatives, Republicans control the senate, and not one Republican member in the upper chamber has signalled support for kicking Mr Trump out of office. An impeachment conviction in the senate requires 67 votes out of 100.

Democrats argue that Mr Trump acted improperly when he pressed Ukraine's president Volodymyr Zelenskiy to open an investigation of former US vice president Joe Biden and his son's dealings in the eastern European nation. The ex-vice president's son, Hunter Biden, sat on the board of a Ukrainian energy company.

Joe Biden is widely regarded as one of the front-runners for the Democratic nomination in next year's presidential election.

US house intelligence committee chairman Adam Schiff said: "The evidence that we have found is really quite overwhelming that the president used the power of his office to secure political favours and abuse the trust American people put in him and jeopardise our security.

"It was a difficult decision to go down this road, because it's so consequential for the country."

Mr Schiff added that "the president was the author of his own impeachment inquiry by repeatedly seeking foreign help in his election campaigns.

"Americans need to understand that this president is putting his personal political interests above theirs. And that it's endangering the country."

Mr Trump is currently in London at a meeting of Nato leaders, where he is preparing to meet German chancellor Angela Merkel, Italian PM Giuseppe Conte and Danish leader Mette Frederiksen on the sidelines.

On Tuesday, Mr Trump insisted: "The impeachment is going nowhere.

"It is a waste of time. They're wasting their time. And it's a disgrace. It's a disgrace to our country."

He went on to call the impeachment effort by Democrats "unpatriotic", and said he would not be watching Wednesday's hearing.

The session in the US house will delve into possible impeachable offences, but the real focus will be on the panel, led by chairman Jerrold Nadler, and made up of a sometimes boisterous, sharply partisan division of members of congress.

In a 53-page opening statement obtained by the Associated Press, Republican witness Jonathan Turley, a law professor at George Washington University, will say that the Democrats are bringing a "slipshod impeachment" case against the president based on second-hand information. However, Mr Turley does not excuse the president's behaviour.

"It is not wrong because President Trump is right," according to Mr Turley. He referred to Mr Trump's call with Ukraine as "anything but 'perfect', as the president claims".

"A case for impeachment could be made, but it cannot be made on this record," he added.

The remaining three witnesses, all called by Democrats, will argue for impeachment, according to statements obtained by reporters.

Michael Gerhardt of the University of North Carolina at Chapel Hill argues: "If congress fails to impeach here, then the impeachment process has lost all meaning."

The political risks are high for all parties as the house presses only the fourth presidential impeachment inquiry in US history.

The Trump-Ukraine Impeachment Inquiry Report provides a detailed account of a shadow diplomacy run by Mr Trump's lawyer Rudy Giuliani, resulting in layers of allegations that can be distilled into specific acts, like bribery or obstruction, and the more amorphous allegation that Mr Trump abused his power by putting his interests above the nation.

Based on two months of investigation sparked by an anonymous government whistleblower's complaint, the report relies heavily on testimony from current and former US officials who defied White House orders not to appear.

The inquiry found that Mr Trump "solicited the interference of a foreign government, Ukraine, to benefit his reelection," Mr Schiff wrote in the report's preface.

In doing so, the president "sought to undermine the integrity of the US presidential election process, and endangered US national security".

Possible grounds for impeachment are focused on whether Mr Trump abused his office as he pressed Ukrainian leader Volodymyr Zelenskiy to open investigations into Mr Trump's political rivals.

At the time, Mr Trump was withholding military aid, jeopardising key support as Ukraine faces an aggressive Russia at its border.

The report also accuses Mr Trump of obstruction, becoming the "first and only" president in US history to "openly and indiscriminately" defy the house's constitutional authority to conduct the impeachment proceedings by instructing officials not to comply with subpoenas for documents and testimony.