Biden released the statement after news organizations reported Trump had urged Zelenskiy to probe the activities of Biden's son Hunter, who worked for a Ukrainian gas company.
Giuliani's CNN appearance came as tensions grew over reports that said Trump made an unspecified "promise" to a foreign leader, which reportedly prompted an unidentified official within the intelligence community to file a whistleblower complaint. "If the president has done what has been alleged, then he is stepping into a unsafe minefield with serious repercussions for his administration and our democracy".
But there has been a flurry of recent disclosures related to Trump and top advisers on Ukraine that are drawing scrutiny.
Asked whether he'd discussed Biden with Ukraine's Zelensky during a phone call in late July, Trump said it "doesn't matter what I discussed", but insisted that someone should look into Biden.
"Multiple reports now suggest that the so-called whistleblowers claim it surrounds the country of Ukraine", Hannity said on his program Friday night.
The Wall Street Journal, meanwhile, quoted sources as saying Mr Trump had urged Mr Zelensky about eight times to work with his lawyer Rudy Giuliani on an investigation into Mr Biden's son, but had not offered anything in return. Giuliani's efforts have sparked anger among Democrats who have claimed that Trump, in the aftermath of special counsel Robert Mueller's Russian Federation investigation, may have asked for foreign assistance in his upcoming reelection bid. Giuliani cancels the trip amid criticism but continues his lobbying campaign over ensuing months.
No-one in Ukraine's presidential administration wants to talk about the 25 July phone call between Mr Trump and Mr Zelensky, or respond to the claims that Mr Trump asked Ukraine to investigate his possible opponent in 2020 in return for continued United States military support. The Ukrainian readout describes Trump as "convinced that the new Ukrainian government will be able to quickly improve image of Ukraine, complete investigation of corruption cases, which inhibited the interaction between Ukraine and the US".
According to a readout released from the White House, Trump spoke with Zelensky on July 25 "to congratulate him on his recent election". But, apparently for the first time since the whistle-blower law's passage, that did not occur, on the grounds that "the complaint concerns conduct by someone outside of the Intelligence Community and because the complaint involves confidential and potentially privileged communications".
U.S. policy of ‘maximum pressure’ will fail, Iran’s Supreme Leader vows
President Trump is "obligated to try and find peace", he said. "I'm somebody that would like not to have war", he said. Iran's Foreign Ministry spokesman Abbas Mousavi dismissed Washington's accusations, calling them "blind and futile".
Atkinson made clear that he disagreed with a lawyer for the Office of the Director of National Intelligence, who had contradicted the inspector general and found that the whistleblower complaint did not meet the statutory definition of an urgent concern because it involved a matter not under the DNI's jurisdiction.
Concerns were already been brewing on Capitol Hill about whether the administration was holding up a military assistance package to Ukraine as part of a political quid pro quo.
Atkinson told lawmakers that he disagreed with that analysis - meaning he felt the matter was under the DNI's purview - and also that it was urgent "in the common understanding of the word", the person said. The panel is laden with Republicans sympathetic to Ukraine.
Schiff had issued a subpoena to Maguire last week in an attempt to force him to turn over the whistleblower's complaint.
Schiff said the Justice Department had misinterpreted the law in blocking Maguire from disclosing the complaint. A hearing is slated for September 26.
"I didn't ask them to look into Joe Biden", Giuliani told host Christopher Cuomo on Thursday.