Washington, Oct 1 (AFP) The Trump administration pushed back hard Tuesday against the impeachment investigation of the president, accusing Democrats of bullying and intimidation in asking five diplomats to testify on White House efforts to seek dirt on a Trump political rival.

Secretary of State Mike Pompeo questioned the authority of three House committees conducting the impeachment probe to summon testimony from the diplomats and said they would not appear to testify in the coming week as requested.

He also challenged the Democrat-led committees' right to demand documents from them and suggested the administration was prepared to take the fight to court.

The committees' request "can be understood only as an attempt to intimidate, bully and treat improperly the distinguished professionals of the Department of State," Pompeo said in a letter to Congress.

"I will not tolerate such tactics, and I will use all means at my disposal to prevent and expose any attempts to intimidate the dedicated professionals whom I am proud to lead."

Pompeo's push-back came after Trump's personal lawyer Rudy Giuliani suggested he might not comply with a subpoena issued Monday by the three committees.

They want the former New York mayor to produce documents related to his efforts on Trump's behalf to pressure Ukraine President Volodymyr Zelensky to provide dirt on Trump's potential 2020 election rival, Democrat Joe Biden.

Giuliani alleged that the heads of the House Intelligence, Foreign Affairs and Oversight Committees had "prejudged" the case.

"It raises significant issues concerning legitimacy and constitutional and legal issues including, inter alia, attorney client and other privileges. It will be given appropriate consideration," he said of the subpoena.

The moves strongly indicated that the administration is preparing lines of resistance against the abuse of power investigation led by House Intelligence Committee Chairman Adam Schiff.

Pompeo's letter suggested that the committees could be forced to subpoena the five diplomats, and that the State Department and White House could seek to limit what they can talk about.

Schiff launched the impeachment probe on Friday after a White House summary memo of Trump's July 25 call with Zelensky supported a whistleblower's allegations that Trump tried to enlist Ukraine's help in his fight for reelection next year, and then tried to hide the fact.

Pompeo was one of several people who listened to the call, in which, according to the official record, Trump spoke of little but his desire for Ukraine's help against Biden.

Schiff's first act was to subpoena Pompeo for documents related to communications with Ukraine and to interview the five current or former diplomats.

They include Marie Yovanovitch, who was removed earlier this year as US ambassador in Kiev after she reportedly resisted helping the administration pressure Zelensky.

They also include Kurt Volker, who was the US special envoy to Ukraine and was involved in Giuliani's efforts to obtain Kiev's cooperation.

The committees said they were "investigating the extent to which President Trump jeopardized national security by pressing Ukraine to interfere with our 2020 election and by withholding security assistance provided by Congress to help Ukraine counter Russian aggression."

Trump, meanwhile, has stepped up his ad hominem attacks on Schiff and others involved in the impeachment probe.

On Monday, he said the White House was trying to get more information on the anonymous whistleblower, whose identity is protected by law.

Trump, who has suggested Schiff be arrested for treason, on Friday tweeted: "It is just another Democrat Hoax!"

"Why isn't Congressman Adam Schiff being brought up on charges for fraudulently making up a statement and reading it to Congress," he asked.

But politicians from both parties warned Trump against threatening or attempting to unmask the whistleblower, who was reported to be a CIA analyst.

"This person appears to have followed the whistleblower protection laws and ought to be heard out and protected," said Republican Senator Chuck Grassley. (AFP)

(This is an unedited and auto-generated story from Syndicated News feed, LatestLY Staff may not have modified or edited the content body)