The US House of Representatives voted Wednesday to transmit articles of impeachment against President Donald Trump to the Senate, opening the way for the historic trial of the 45th president for abuse of power.In a strict party-line vote, the House approved a resolution appointing seven Democratic impeachment managers - the prosecution team for the trial - and empowered them to deliver the two charges against Trump to the Senate later in the day.House Speaker Nancy Pelosi repeated her demand that the Senate trial call witnesses from Trump's inner circle to testify and subpoena documents that were refused to the original investigation, warning the body will be guilty of a "cover-up" if it does not do so."My colleagues on both sides of the aisle, we are here today to cross a very important threshold in American history," Pelosi said before the vote."Whatever the outcome, the American people want a fair trial." The momentous trial, expected to begin Tuesday in the Republican-controlled Senate and last several weeks, will be only the third ever of an American president, and will decide whether Trump is forced from office.Before the vote, Trump, who has labelled the House impeachment a political witch hunt, accused Democrats of a "con job.""Here we go again, another Con Job by the Do Nothing Democrats," he wrote on Twitter.Grave taskEarlier Wednesday Pelosi chose seven Democratic legislators to prosecute the case against Trump.Adam Schiff, the House Intelligence Committee Chairman who headed the impeachment investigation, will lead the group.In addition to Schiff, the prosecution team will include Judiciary Committee Chair Jerry Nadler, House Democratic Caucus Chair Hakeem Jeffries, and four other senior Democrats, most of them with prosecutorial experience in the US justice system."The task before us is a grave one but one demanded by our oath," Schiff said on the House floor."President Trump put his own personal interests above the national interest, above our national security. And if not stopped he will do it again," he said."The only remedy is the conviction and removal from office of President Donald Trump."Today, we take the next step to #DefendOurDemocracy, sending articles of impeachment to the Senate.McConnell will have a choice: stand with the Constitution, or with Trump’s cover-up.Uphold the rule of law, or help Trump undermine it.— Adam Schiff (@RepAdamSchiff) January 15, 2020The Managers of the impeachment trial of the President are public servants committed to protecting our Constitution – and have the litigation and courtroom experience necessary to execute this task. They will #DefendOurDemocracy. pic.twitter.com/nsGtEVh59n— Nancy Pelosi (@SpeakerPelosi) January 15, 2020It looks like today’s the day. House Democrats may finally stand behind the rushed, unfair, and nakedly partisan impeachment that they themselves delayed for four weeks. The ‘prosecutors’ have finally overcome their cold feet.— Leader McConnell (@senatemajldr) January 15, 2020U.S. House APPROVES Impeachment Managers and to send Articles of Impeachment to the Senate, 228-193. Full video here: https://t.co/TCjCWIM7gG pic.twitter.com/yMhDz3YIDr— CSPAN (@cspan) January 15, 2020 'Crazy witch hunt' Trump is accused of secretly holding up aid to Ukraine between July and September to pressure Kiev to investigate former vice president Joe Biden, the Democratic frontrunner in this year's White House race.He was formally impeached on December 18 when the Democratic-controlled House charged him with abusing his power by illicitly seeking help from Ukraine for his reelection. The president is also charged with obstruction for holding back witnesses and documents from the House impeachment investigation in defiance of Congressional subpoenas.The articles of impeachment will be walked from the House to the Senate later Wednesday, at around 5 pm (2200 GMT), in a solemn procession seen only twice before in US history.But their reading out loud to senators, officially placing the president on trial, is only expected Thursday.Trump's conviction in the Senate is highly unlikely as the president's Republican Party has a 53-47 majority. A two-thirds super-majority of senators is required to find him guilty and remove him from office.According to a senior administration official, the White House believes it has an easy case and that the Senate will quickly acquit.The official said the trial was "extraordinarily unlikely" to run more than two weeks.New evidenceDemocrats continued to challenge the Senate to bring in high-level witnesses they believe will support the evidence against Trump.They especially want to hear from Trump's chief of staff Mick Mulvaney and former national security advisor John Bolton. Bolton, who other officials have testified was angered by the scheme to pressure Ukraine for Trump's domestic political needs, has volunteered to testify if subpoenaed."We should have witnesses, and we should have documents," Pelosi said.On Tuesday Democrats released newly-acquired files that showed Trump's personal lawyer Rudy Giuliani working with Ukrainian-born American Lev Parnas early last year to pressure Kiev to investigate Biden.They also showed the two, working with Ukrainian officials, trying to force out the US ambassador to the country, Marie Yovanovitch, eventually removed by Trump.The documents "demonstrate that there is more evidence relevant to the president's scheme, but they have been concealed by the president himself," Democrats said in a statement.Battle over calling witnesses But Senate Majority Leader Mitch McConnell, whose solid Republican majority will set the rules for Trump's trial, has refused to agree to invite witnesses before opening statements and arguments are delivered.After the articles are received at the Senate, Supreme Court Chief Justice John Roberts will be sworn in to preside over the process, on either Thursday or Friday.Roberts will then swear in the 100 senators who will act as the jury and be required to remain in the body for all the time the trial is underway.