President Donald Trump speaks during an event on "transparency in Federal guidance and enforcement" in the Roosevelt Room of…
President Donald Trump speaks during an event on "transparency in Federal guidance and enforcement" in the Roosevelt Room of the White House, Oct. 9, 2019, in Washington.

President Donald Trump predicts his impeachment battle with House Democrats will wind up before the U.S. Supreme Court.

The president spoke to reporters Wednesday, a day after the White House says it is refusing to participate in the Democratic-led inquiry into whether he should be impeached.

Trump did not say exactly what House leaders must do if they want his cooperation. But he said he would cooperate "if they give us our rights" and Republicans "get a fair shake."

On Twitter, he called the impeachment probe a "Total Scam by the Do Nothing Democrats."

Among the gripes spelled out in the White House letter is a complaint that Democrats are denying Trump and his Republican supporters in the House the opportunity to question witnesses and see the evidence the Democrats have.

The White House calls the impeachment inquiry "unconstitutional" and demands the full House be allowed to vote on whether there should be an inquiry.

But there is no rule preventing the House from looking into allegations of illegal activity by a president before deciding whether to bring actual articles of impeachment to a vote.

Speaker of the House Nancy Pelosi, D-Calif., is surrounded by reporters as she arrives to meet with her caucus at the Capitol in Washington, after declaring she will launch a formal impeachment inquiry against President Donald Trump.

Speaker of the House Nancy Pelosi called the White House letter "the latest attempt to cover up his (Trump's) betrayal of our democracy and to insist that the president is above the law."

She says Democrats would consider a refusal to cooperate more evidence of obstruction.

Earlier Tuesday, Democratic presidential candidate Joe Biden for the first time bluntly called for Trump's impeachment.

"Donald Trump has violated his oath of office, betrayed this nation, and committed impeachable acts," Biden said in New Hampshire.

Trump replied by saying Biden is "falling like a rock. I don't think he's going to make it," the president said in apparent reference to Biden's recent slippage in the polls.

Trump has accused Biden of corruption, alleging that when he was vice president, he threatened to withhold loan guarantees to Ukraine unless the government stops investigating a gas company for which Biden's son, Hunter, held a seat.

There is no evidence of any wrongdoing by Joe or Hunter Biden.

But a U.S. intelligence whistleblower expressed concern to the inspector general about a July 25 telephone call between Trump and Ukrainian President Volodymyr Zelenskiy. During that call, Trump urged Zeleinskiy to open an investigation into Biden in an effort to dig up dirt on a rival for the White House.

A second whistleblower and a series of texts by diplomats working to assist Ukraine in carrying out Trump's wishes seem to corroborate the first whistleblower's complaint.

FILE - Gordon Sondland, the United States Ambassador to the European Union, addresses the media at the U.S. Embassy to Romania in Bucharest, Sept. 5, 2019.

Although soliciting foreign government interference in a U.S. election is a potentially impeachable offense, Democrats are focused on whether Trump withheld $400 million in badly needed aid to Ukraine in exchange for its cooperation in a Biden probe.

The State Department Tuesday refused to allow Trump donor and U.S. Ambassador to the European Union Gordon Sondland to voluntarily speak to lawmakers about what he may know about a possible "quid pro quo" with Ukraine, forcing House leaders to subpoena him to testify.

Former U.S. Ambassador to Ukraine, Marie Yovanovitch, is scheduled to testify later this week.