Charge d'Affairs of the U.S. Embassy in Ukraine William Taylor (R) and deputy assistant secretary of State for European and Eurasian affairs George Kent swear before the U.S. House Committee on Intelligence during the impeachment hearings on President Donald Trump on Capitol Hill in Washington D.C. the United States, Nov. 13, 2019. The U.S. House Committee on Intelligence held the first public hearing Wednesday since House Democrats launched an impeachment inquiry into President Donald Trump in September to determine whether he abused his office in his interactions with Ukraine. (Xinhua/Liu Jie)

 
Two top US diplomats delivered gripping testimony on Wednesday about Donald Trump's efforts to get Ukraine to investigate his potential 2020 rival Joe Biden, as the impeachment inquiry into the president shifted into a new phase of high-stakes televised hearings.

Trump dismissed the probe in the Democratic-led House of Representatives as a "witch hunt" and said he was "too busy" to watch the first public hearings, during which he received staunch backing from Republican lawmakers.

William Taylor, the top US diplomat in Ukraine, began his testimony before the House Intelligence Committee with a new revelation about Trump's efforts to pressure Kiev - the main issue of just the fourth impeachment process in US history.

Democrats accuse Trump of abusing his power by using US military assistance and a possible White House meeting to pressure President Volodymyr Zelensky into opening a probe into the Democrat Biden and his son Hunter, who served on the board of Ukrainian gas company Burisma.

The key evidence is the official White House transcript of a July 25 telephone call between Trump and Zelensky, in which the US president asked his Ukrainian counterpart to investigate the Bidens. Taylor testified that he was told Trump cared more about the probe than he did about Ukraine.

The grey-haired former army officer and veteran diplomat, who testified in a closed hearing last month, said he had since become aware of a telephone call between Trump and the US' EU Ambassador Gordon Sondland, which a ­member of Taylor's staff overheard.

The staffer asked Sondland after the call what Trump thought about Ukraine and was told that "President Trump cared more about the investigations of Biden," Taylor said.

Asked about the new allegations, while hosting his Turkish counterpart Recep Tayyip Erdogan at the White House, Trump replied, "First time I've heard it." 

Sondland "did speak to me for a brief moment, and I said no quid pro quo under any circumstances." 

If the House impeaches Trump, it would then go to trial in the Senate, where Republicans enjoy a 53-47 majority.

The next hearing is scheduled for Friday.