The House is set to vote Wednesday to send the articles of impeachment against President Donald Trump to the Senate for a landmark trial on whether the charges of abuse of power and obstruction of Congress are grounds for his removal.

Speaker Nancy Pelosi plans a morning announcement to name the House managers who will prosecute the case, a month after the House voted to impeach Trump. At midday, the House will vote to send the impeachment articles to the Senate, and the managers will later in the day walk them across the Capitol to the Senate.

Trump's trial will be only the third presidential impeachment trial in U.S. history, and it comes against the backdrop of a politically divided nation and an election year.

He was impeached by the Democratic-led House last month on charges of abuse of power over pushing Ukraine to investigate Democratic rival Joe Biden as president withheld aid from the country, and obstructing Congress's ensuing probe.

New details of Trump's efforts on Ukraine emerged late Tuesday, increasing pressure on senators to call witnesses in the trial, a step that Senate majority leader Mitch McConnell has been reluctant to take.

House investigators announced they were turning over a "trove" of new records of phone calls, text messages and other information from Lev Parnas, an associate of Trump lawyer Rudy Giuliani.

Intelligence committee chair Adam Schiff said the information shows Trump's effort `'to coerce Ukraine into helping the president's re-election campaign." He said this and other new testimony must be included in the Senate trial.

The Senate is expected to transform into an impeachment court as early as Thursday, although significant proceedings wouldn't begin until next Tuesday after the Martin Luther King Jr. holiday. The Constitution calls for the chief justice to preside over senators, who serve as jurors, to swear an oath to deliver "impartial justice."

Division over witnesses

McConnell, who is negotiating rules for the trial proceedings, said all 53 Republican senators are on board with his plan to start the session and consider the issue of witnesses later.

Senate Republicans also signalled they would reject the idea of simply voting to dismiss the articles of impeachment against Trump, as Trump himself has suggested. McConnell agreed he does not have the votes to do that.

"There is little or no sentiment in the Republican conference for a motion to dismiss," McConnell said Tuesday. `'Our members feel we have an obligation to listen to the arguments."

A mounting number of senators say they want to ensure the ground rules include the possibility of calling new witnesses.

Sen. Susan Collins of Maine is leading an effort among some Republicans, including Mitt Romney of Utah and Lisa Murkowski of Alaska for witness votes.

Romney said he wants to hear from John Bolton, the former national security adviser at the White House, who others have said raised alarms about the alternative foreign policy toward Ukraine being run by Giuliani.

Democrats have been pushing Republicans, who have a slim Senate majority, to consider new testimony, arguing fresh information has emerged during Pelosi's monthlong delay in transmitting the charges.

Republicans control the chamber, 53-47, and are all but certain to acquit Trump. It takes just 51 votes during the impeachment trial to approve rules or call witnesses. Just four GOP senators could form a majority with Democrats to insist on new testimony. It also would take only 51 senators to vote to dismiss the charges against Trump.

At Tuesday's Republican lunch, Sen. Rand Paul of Kentucky warned that if witnesses are allowed, defence witnesses could also be called. He and other Republicans want to subpoena Biden and his son, Hunter, who served on the board of a gas company in Ukraine, Burisma, for over two years while his father was U.S. vice-president.

McConnell is drafting an organizing resolution that will outline the steps ahead. Approving it will be among their first votes of the trial, likely next Tuesday.

According to a report by U.S. company Area 1 Security, members of the Russian GRU intelligence directorate launched a phishing campaign against Ukrainian gas company Burisma Holdings in November, just as impeachment proceedings were heating up against U.S. President Donald Trump. Blake Darché, chief strategy officer for Area 1, spoke to As It Happens host Carol Off about the hack. 5:59

He prefers to model Trump's trial partly on the process used for then-President Bill Clinton's trial in 1999. It, too, contained motions for dismissal or calling new witnesses.

McConnell is hesitant to call new witnesses who would prolong the trial and put vulnerable senators who are up for reelection in 2020 in a bind with tough choices. At the same time, he wants to give those same senators ample room to show voters they are listening to demands for a fair trial.

Most Republicans now appear willing to go along with McConnell's plan to start the trial first then consider witnesses later, rather than upfront, as Democrats want.