Ex-National Security Adviser Bolton Willing to Testify at Trump Impeachment TrialFormer U.S. national security adviser John Bolton said Monday he would testify at President Donald Trump's impeachment trial if the Senate subpoenas him, potentially giving Democrats key behind-the-scenes testimony about Trump's efforts to get Ukraine to launch investigations to benefit himself politically. Bolton, a tough advocate for U.S. power across the globe, served for 17 months as Trump's third top security aide until the president ousted him last September amid increasing rancorous disagreements over how the U.S. should handle its contentious relations with Iran, North Korea and Afghanistan. In the run-up to the House of Representatives vote last month to impeach Trump, investigators decided to not subpoena Bolton, fearful of a long legal battle in U.S. courts over whether he would have to testify or could adhere to Trump's directive banning testimony by key aides, some of whom honored the president's edict while others did not. A tandem case with the same issues involving the potential testimony of a Bolton aide, Charles Kupperman, was left unresolved as Democratic lawmakers advanced their case against Trump, approving two articles of impeachment. But as Trump's impeachment trial looms in the Senate, even though no date has been set in a congressional stalemate over the trial's parameters, Bolton said in a statement he had to "resolve the serious competing issues as best I could, based on careful consideration and study." He said, "I have concluded that, if the Senate issues a subpoena for my testimony, I am prepared to testify." Bolton was at the center of significant White House foreign policy debates, including Trump's efforts to press Ukrainian President Volodymyr Zelenskiy to open investigations of one of Trump's top 2020 Democratic challengers, former Vice President Joe Biden, his son Hunter's work for a Ukrainian natural gas company and a debunked conspiracy theory that Ukraine attempted to undermine Trump's 2016 election campaign. At one point during the House impeachment investigation, Bolton's lawyer said that his client had "personal knowledge" of relevant Ukraine-related meetings and conversations "that have not yet been discussed in testimonies thus far." Bolton is one of four Trump White House aides that Senate Democratic leader Chuck Schumer says should be called to testify at the impeachment trial. But Senate Majority Leader Mitch McConnell, who is coordinating trial strategy with Trump's White House lawyers, has balked at calling any witnesses in hope that after the Senate hears the House arguments against Trump and the president's defense, it would then vote quickly to acquit him. U.S. lawmakers have returned to Washington after their holiday recess, but they are no closer to deciding when and how Trump's impeachment trial would be staged. Key lawmakers remain stalemated over impeachment, now complicated by congressional debate over the merits of Trump's approval of the drone attack that killed a key Iranian general, Qassem Soleimani, last week outside the Baghdad airport. House Speaker Nancy Pelosi, leader of the Democrat-controlled House, is refusing to send two articles of impeachment to the Senate until she believes it would conduct a fair trial. One article accuses Trump of abusing the power of his presidency to pressure Ukraine to launch an investigation into the Bidens, while the other alleges he obstructed congressional efforts to investigate his Ukraine-related actions. As Trump and aides pressed Ukraine for the Biden investigations, Trump was temporarily withholding $391 million in military aid Ukraine wanted to help fight pro-Russian separatists in eastern Ukraine. Trump eventually released the military assistance to Ukraine last September without Zelenskiy opening the Biden investigations. Republicans say that is proof Trump did not engage in a reciprocal quid pro quo deal with Ukraine. McConnell says the Senate cannot hold an impeachment trial without receiving the impeachment allegations from the House, although some Republican senators looking to acquit Trump as quickly as possible now say the Senate should start the trial anyway. Schumer has sparred with McConnell to try to win assurances that key Trump White House aides will be allowed to testify at the impeachment trial, which would be only the third such impeachment proceeding in U.S. history. But McConnell, advocating Trump's quick acquittal, has refused so far to guarantee that acting White House chief of staff Mick Mulvaney, Bolton and others would testify. Schumer said Sunday he remains "hopeful" that four Republican senators will vote against McConnell and join with the minority bloc of 47 Democrats to vote to hear testimony from the Trump aides. Meanwhile, Trump again ridiculed the impeachment effort on Monday, which was approved with near unanimous Democratic support in the House. "To be spending time on this political Hoax at this moment in our history, when I am so busy, is sad!" he said on Twitter. “The reason they are not sending the Articles of Impeachment to the Senate is that they are so weak and so pathetic.” @LindseyGrahamSC @MariaBartiromo The great Scam continues. To be spending time on this political Hoax at this moment in our history, when I am so busy, is sad! He added, "The Impeachment Hoax, just a continuation of the Witch Hunt which started even before I won the Election, must end quickly. Read the Transcripts, see the Ukrainian President’s strong statement, NO PRESSURE - get this done. It is a con game by the Dems to help with the Election!" The Impeachment Hoax, just a continuation of the Witch Hunt which started even before I won the Election, must end quickly. Read the Transcripts, see the Ukrainian President’s strong statement, NO PRESSURE - get this done. It is a con game by the Dems to help with the Election! "Congress & the President should not be wasting their time and energy on a continuation of the totally partisan Impeachment Hoax when we have so many important matters pending. 196 to ZERO was the Republican House vote, & we got 3 Dems. This was not what the Founders had in mind!" Congress & the President should not be wasting their time and energy on a continuation of the totally partisan Impeachment Hoax when we have so many important matters pending. 196 to ZERO was the Republican House vote, & we got 3 Dems. This was not what the Founders had in mind! When a trial finally occurs, the Senate will almost certainly acquit Trump. A two-thirds majority in the 100-member Senate would be required to convict Trump to remove him from office, meaning at least 20 Republicans would have to turn against the president if all 47 Democrats also vote to convict him. Some Republican lawmakers have voiced objections to Trump's request to Zelenskiy for the investigation of former Vice President Biden, who leads national polls to oppose Trump in the November presidential election. But no Republican lawmakers have called for Trump's conviction and removal from office.