The new subpoenas follow those issued to the State Department and White House in recent weeks by the House Intelligence, Oversight and Foreign Affairs Committees.
A parade of USA 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.
On Sunday, lawyers said a second whistleblower had come forward to substantiate an August complaint from an unnamed US government official, which touched off the investigation.
Earlier, ABC News reported that the new whistleblower has direct knowledge of the complaint centered on the call between Trump and the president of Ukraine in which Trump allegedly used the power of his office to enlist a foreign country to interfere in the 2020 USA election.
Trump and his supporters have rejected the accusations he did anything improper. Biden, the former vice president who is seeking the 2020 Democratic nomination, joined the chorus of condemnation, tweeting that Trump "must stop stonewalling Congress". The White House released a summary of the call.
Democrats also have called a number of US diplomats to Capitol Hill for closed-door testimony this week as they build their impeachment case against Trump, while the White House considers ways to slow down the process.
Trump has alleged that Hunter Biden profited in his business dealings in both Ukraine and China from his father's position, and that Joe Biden, as vice president, pushed Ukraine to fire a prosecutor to impede a probe of a company tied to his son. Though the timing raised concerns among anti-corruption advocates, there has been no evidence of wrongdoing by either Biden.
"I think this is a nightmare for the Biden campaign", Graham said. Romney had said on Twitter that "By all appearances, the President's brazen and unprecedented appeal to China and to Ukraine to investigate Joe Biden is wrong and appalling".
"Mr. President, you are not above the law". Trump wrote at one point, continuing to paint himself as the victim of a "deep state" and hostile Democrats.
A protesters, right, holding a banner blows a whistle as the motorcade of President Donald Trump arrives at the Trump National Golf Club in Sterling, Va., Saturday, Oct. 5, 2019. Mitt Romney, one of the few Republicans who has publicly questioned Trump's conduct.
"The Democrats are lucky that they don't have any Mitt Romney types", Trump wrote, painting the former Republican nominee as a traitor to his party.
"The White House should be warned that continued efforts to hide the truth of the President's abuse of power from the American people will be regarded as further evidence of obstruction", she said in a statement Tuesday night.
"The reporting that a second whistleblower has come forward or is about to come forward, I believe again would be someone who sees wrongdoing, hears wrongdoing and wants to do something about it", Demings said.
The impeachment investigation could lead to the approval by the Democratic-led House of formal charges against Trump. Those remarks that prompted a response from Trump Sunday morning.