WASHINGTON (REUTERS) - A parade of United States diplomats will head to Capitol Hill for closed-door testimony this week as Democrats build their impeachment case against President Donald Trump, while the White House considers ways to slow down the process.
The interviews could yield more fodder for Democrats' impeachment drive over a whistle-blower's allegations that Mr Trump leveraged US$400 million (S$552 million) in aid to secure a promise from Ukrainian President Volodymyr Zelensky to investigate political rival Joe Biden, and his son Hunter, who sat on the board of a Ukrainian energy company.
Mr Trump has denied wrongdoing and assailed the probe.
Among those due to testify are Mr Gordon Sondland, the US ambassador to the European Union who was involved in efforts to get Ukraine to open the investigations, and Ms Masha Yovanovitch, who was abruptly recalled from her post as US ambassador to Ukraine in May after Trump supporters questioned her loyalty to the President.
Mr Trump's White House could formally tell House Speaker Nancy Pelosi as early as Monday that it will ignore lawmakers' demands for documents until the Democratic-controlled House of Representatives holds a vote to formally approve the impeachment inquiry.
Ms Pelosi says a vote is not needed, but Democrats say she would prevail if one were held, although very few Republicans would be expected to side with the Democratic majority. Congress returns to Washington on Oct 15 after a two-week recess.
"There's no question in my mind that she would have the votes," Democratic Representative Jim Himes said on CBS' Face The Nation on Sunday.
The impeachment investigation could lead to the approval by the House of formal charges against Mr Trump.
A trial on whether to remove him from office would then be held in the Republican-controlled Senate, but few Republicans have broken rank with Mr Trump so far for asking Ukraine and China to launch investigations of Mr Biden, a former vice-president and leading contender for the Democratic nomination to face Mr Trump in the November 2020 presidential election.
SECOND WHISTLE-BLOWER
On Sunday, lawyers said a second whistle-blower had come forward to substantiate an August complaint from an unnamed US government official, which touched off the investigation.
Diplomatic text messages released by Democrats last week show that US officials were involved in the effort to secure a public commitment from Ukraine to look into the business dealings of Mr Hunter Biden.
Mr Trump has alleged that Mr Hunter Biden profited in his business dealings in both Ukraine and China from his father's position, and that Mr Joe Biden, as vice-president, pushed Ukraine to fire a prosecutor to impede a probe of a company tied to his son.
There has been no evidence of wrongdoing on the part of either Biden.
Those texts show Mr Sondland seeking to downplay the concerns of another US diplomat, Mr William Taylor, that the US was withholding US$400 million in aid in order to secure Ukraine's cooperation.
"The President has been crystal clear no quid pro quo's of any kind," Mr Sondland wrote. "I suggest we stop the back and forths by text."
Mr Sondland is expected to testify on Tuesday before the three House committees leading the impeachment probe. State Department counsellor Ulrich Brechbuhl is also scheduled to testify that day.
Deputy Secretary of State George Kent is scheduled to testify on Monday. Ms Yovanovitch is due to appear on Friday.
