US President Donald Trump faces a high likelihood of being impeached and tried in Congress in the coming weeks on accusations that he coerced Ukraine into assisting his reelection efforts.

Lawmakers have heard public testimony from 12 witnesses supporting allegations that Trump pressured Kiev to announce investigations into this political rivals, including leading Democrat Joe Biden. 

The president stalled almost $400 million in military aid and a White House visit for new Ukrainian president Volodymyr Zelensky, allegedly to strong-arm Kiev - which is at war with Russia - into helping.

The House Intelligence Committee has not formally concluded its role in the inquiry, possibly waiting for a court ruling on Monday that could empower members to force senior Trump aides to testify.

But Democrats appear determined to hold an impeachment vote in the House of Representatives by the end of the year, which could see Trump go on trial in the Senate in January.

The steps of the process:

Articles of impeachment

The Intelligence Committee will compile a report on its findings for the House Judiciary Committee, whose members will debate the evidence and possibly interview their own witnesses. 

Unlike in the initial fact-finding phase, Trump and his attorneys can take part, submitting testimony, attending the hearings, reviewing the evidence and questioning witnesses.

Trump said last week he might be willing to answer questions in writing.

At the end the panel will vote on formal articles of impeachment, the political equivalent of an indictment. 

The US Constitution's definition of impeachable offenses is broad: "treason, bribery, or other high crimes and misdemeanors." Those are not defined, and generally seen to encompass abuse of power and the public trust.

Democrats are weighing four counts, according to reports: abuse of power for pressuring Ukraine for domestic political help; bribery for holding out aid and a summit for the help; contempt of Congress for refusing to comply with subpoenas; and obstruction of justice.

The House impeachment vote

The articles of impeachment passed by the Judiciary Committee will then be sent to the entire House for a vote.

Representatives will debate the charges in a phase that could take some time: in the 1988 impeachment of president Bill Clinton, House members spent more than 13 hours over two days arguing the case.

Passing the articles -- or "impeaching" the president -- requires a simple majority of the House. Democrats have control, with 233 members to the Republicans' 197, and the party has shown a united front, meaning approval is widely expected.

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Trial in the Senate

A vote to impeach would send the case to a Senate trial of a sitting president for only the third time in US history.

The chief justice of the Supreme Court would preside, and the 100 senators would sit as the jury. Representatives from the House would act as prosecutors, with the president's attorneys presenting his defense.

Convicting Trump could be difficult, because it would require two-thirds of the Senate, and Republicans hold 53 of the 100 seats.

Senate majority leader Mitch McConnell would control the process, and could keep it short with limited testimony and argument, lasting two weeks or less.

He could also stretch it out: Clinton's trial lasted six weeks and accepted new witness testimony and evidence.

A complicating factor is that six of the Democratic presidential hopefuls are senators and a January trial would hinder their campaigning ahead of the crucial first primary, on February 3 in Iowa.

No matter what the charges are, most analysts say politics has a big influence on the final vote. 

With presidential and congressional elections looming in November 2020, Republican senators especially have to consider whether their constituents will favor voting to remove or protect the Republican president.