Trump Authorizes Release of Transcript of Call with Ukraine's LeaderVOA Ukrainian service reporter Myroslava Gongadze contributed to this report Democratic lawmakers are considering formally launching an impeachment investigation into President Donald Trump Tuesday, following news reports that he froze Congressionally-approved funding for Ukraine while pushing the country to investigate one of his political rivals. Facing mounting pressure, the president pledged Wednesday to release the "complete, fully declassified and unredacted" transcript of his phone call with Ukraine's leader that is at the center of a debate between Congress and the White House over a whistleblower complaint. News reports had said Trump pressured Ukraine's president to investigate leading Democratic presidential candidate Joe Biden and his son, Hunter, who served for years on the board of a Ukrainian gas company. "You will see it was a very friendly and totally appropriate call. No pressure and, unlike (former Vice President) Joe Biden and his son, NO quid pro quo! This is nothing more than a continuation of the Greatest and most Destructive Witch Hunt of all time!," Trump said on Twitter Tuesday. Earlier he confirmed he had told his staff to withhold about $400 million in aid to Ukraine days before a phone call with the Ukrainian President Volodymyr Zelenskiy. "As far as withholding funds, those funds were paid," Trump said. "But my complaint has always been, and I'd withhold again and I'll continue to withhold until such time as Europe and other nations contribute to Ukraine." Trump has insisted he did nothing wrong during the phone call but also acknowledged, "there was pressure put on with respect to Joe Biden. What Joe Biden did for his son, that’s something they should be looking at." Biden to call on Congress to impeach Trump Shortly after Trump spoke Tuesday, Biden's campaign said the former vice president planned to call on Congress to begin impeachment proceedings against Trump if his administration does not begin fully cooperating with ongoing congressional investigations and subpoenas. Democratic Congressman and civil rights icon John Lewis also endorsed impeachment proceedings against Trump, telling colleagues on the House floor Tuesday he has been "patient while we have tried every other path" and warning "the future of our democracy is at stake." The leaders of three House of Representatives committees have demanded Secretary of State Mike Pompeo turn over all documents related to the call Trump made to Zelenskiy. The Democratic chairmen of the House Foreign Affairs, Intelligence, and Oversight committees -- Elliot Engel, Adam Schiff, and Elijah Cummings -- set a Thursday deadline, the same day the intelligence committee is set to hear testimony from acting director national intelligence Joseph Maguire about the whistleblower complaint linked to the call. Zelenskiy and Trump are scheduled to meet Wednesday on the sidelines of the United Nations General Assembly. Zelenskiy told VOA's Ukrainian service Tuesday "we expect support from the U.S." and "We just want the U.S. to always support Ukraine and Ukraine's course in its fight against aggression and war." Zelensky added "I think the meeting will be very warm." Sen. Chris Murphy told reporters Monday that he met several weeks ago with Zelenskiy, and that the Ukranian administration worried the aid cutoff "was a consequence for their unwillingness, at the time, to investigate the Bidens." "They were unwilling to conduct this investigation because there was no merit to it," Murphy said. 'Impeachable offense' \n\nAlso Monday, a group of first-term Democratic members of the House of Representatives with backgrounds in national security wrote an op-ed in the Washington Post saying if the allegations of Trump's actions are true, the lawmakers believe they "represent an impeachable offense." The group includes Reps. Gil Cisneros, Jason Crow, Chrissy Houlahan, Elaine Luria, Mikie Sherrill, Elissa Slotkin and Abigail Spanberger. Trump on Monday dismissed the Democratic drumbeat for impeachment, saying he does not take such threats "at all seriously." He insisted his call with Zelenskiy was a "very nice call," congratulating him on becoming Ukrainian president. Trump said he could very easily release a transcript of the call, and the press would be disappointed. But he refused to commit to doing so, saying it would be a bad precedent. Whistleblower The controversy began last week when reports emerged that an unidentified whistleblower in the national intelligence community became alarmed about a series of actions inside the Trump administration. They include what is now known to be Trump's telephone call with Zelenskiy. This person contacted the intelligence inspector general, who called the complaint "serious" and "urgent." Maguire has refused to turn over the inspector's report to Congress, which the law requires him to do. As vice president under Barack Obama, Joe Biden went to Ukraine in 2016 and threatened to withhold billions of dollars in U.S. loan guarantees unless the government cracked down on corruption. Biden also demanded that Ukraine's chief prosecutor Viktor Shokin be fired. Shokin had previously investigated the gas company on which Hunter Biden served on the board. But the probe had been inactive for a year before Joe Biden's visit. Hunter Biden has said he was not the target of any investigation and no evidence of any wrongdoing by the Bidens has surfaced.