Giuliani threatens legal battle with Mueller over subpoena "If Mueller tries to subpoena us, we're going to court."

The president's lawyer Rudy Giuliani threatened a legal battle with special counsel Robert Mueller if he attempts to subpoena Donald Trump.

"If Mueller tries to subpoena us, we're going to court," Giuliani told ABC News.

His latest comments come on the heels of the publication of a 20-page confidential letter sent by Trump's lawyers to Mueller arguing that the president cannot legally obstruct justice in the Russia investigation due to his position as "chief law enforcement officer."

"It remains our position that the President's actions here, by virtue of his position as the chief law enforcement officer, could neither constitutionally nor legally constitute obstruction because that would amount to him obstructing himself, and that he could if he wished, terminate the inquiry, or even exercise his power to pardon if he so desired," reads the letter dated Jan. 29, which was first obtained and reported by The New York Times.

Although Giuliani was not on the legal team at the time of the letter, he confirmed the contents of the letter to ABC News and said it was delivered to the special counsel in January.

He told ABC News the legal strategy outlined in the letter remains in effect.

Lawyers for Trump and a spokesman for the special counsel declined to comment to ABC News.

Mueller has requested an interview with Trump, but while the president has said he would be willing to sit down with the special counsel, his legal team has advised against it.

Trump tweeted 40 minutes before the New York Times broke the news, questioning whether Mueller's team or the Department of Justice was responsible for leaking the letter.

"There was No Collusion with Russia (except by the Democrats). When will this very expensive Witch Hunt Hoax ever end? So bad for our Country. Is the Special Counsel/Justice Department leaking my lawyers letters to the Fake News Media? Should be looking at Dems corruption instead?"

Echoing Trump, Giuliani accused the special counsel of the leak of the letter, saying that Mueller should have put out a statement condemning it and that he should investigate his team. However, there's no evidence that the letter leaked to the New York Times came from members of the special counsel.

Trump's lawyers also acknowledge for the first time his involvement in dictating that infamous statement about the Trump Tower meeting in 2016, where Trump campaign officials, including his son and son-in-law met with a Russian lawyer who was offering negative information on Hillary Clinton.

"You have received all of the notes communications and testimony indicating that the President dictated a short but accurate response to the New York Times article on behalf of his son, Donald Trump, Jr."

The letter also argues that there is no need for the president to sit for an interview, as the lawyers assert the special counsel has all the information he could possibly need.

"The records and testimony we have, pursuant to the President's directive, already voluntarily provided to your office allow you to delve into the conversations and actions that occurred in a significant and exhaustive manner, including but not limited to the testimony of the President's interlocutors themselves," the letter says. "In light of these voluntary offerings, your office clearly lacks the requisite need to personally interview the President."

Trump's lawyers say that the investigation has interfered with the president's "ability to both govern domestically and conduct foreign affairs," adding "This encumbrance has been only compounded by the astounding public revelations about the corruption within the FBI and Department of Justice which appears to have let to the alleged Russia collusion investigation and the establishment of the Office of Special Counsel in the first place."

John Cohen, an ABC News contributor and former acting undersecretary for intelligence at the Department of Homeland Security, called the letter "highly unusual." Cohen stepped down from his homeland security post in 2014.

"It is highly unusual and extraordinarily unsettling that the lawyer(s) representing the president of the United States would send an official memorandum to a special counsel of DOJ alleging that leadership of the FBI and DOJ is/was corrupt," Cohen told ABC News. "This type of communique has only one purpose and that is to undermine the credibility of those investigating Russia's efforts to engage in an ongoing attack against the U.S. While it may advance the president's political and legal strategy, I fear that it plays into Russia's efforts, which seek to weaken America by undermining the credibility of our national security and law enforcement institutions."