The unrelenting battle between Republican presidential hopefuls Ted Cruz and Donald Trump took a turn for the worse Wednesday when letters surfaced that showed both candidates' attorneys exchanging choice words over the Cruz campaign's latest attack ad against Trump.

On Tuesday, Trump's attorney Jeffrey Goldman sent a cease-and-desist letter to Cruz and two of his senior staffers that threatened a defamation suit if the campaign refuses to remove its negative ad titled, "Supreme Trust." The 30-second TV spot includes footage of an old interview where Trump describes himself as "very pro-choice" and urges voters to think carefully about supporting the billionaire since the next president could be charged with nominating a new Supreme Court justice following the recent death of Justin Antonin Scalia. Scalia was a dominant conservative voice on the bench and his vacancy gives his successor an opportunity to tip the court ideologically.

"Not surprisingly, a closer look at your attack ad reveals that the entire basis of your argument that Mr. Trump is "pro-choice" is based on an interview from "Meet the Press" that took place nearly two decades ago. That's it," Goldman wrote, adding that he "will not sit idly by and allow ... the Cruz campaign to defame Mr. Trump by intentionally disseminating libelous statements ..."

"Toward that end, unless we receive your prompt written assurances that you have stopped running the attack ad, we will seek immediate legal action to prevent the continued broadcast of the attack ad and hold you jointly and severely liable to the fullest extent of the law for any damages resulting therefrom ... and will look forward to doing it," he wrote.

In addition to hold a press conference Wednesday, during which he blasted Trump's "frivolous" legal threat and accused him of enabling the passage of Obamacare by directly donating to Democratic campaign committees, Cruz had his attorney pen a blistering letter to Goldman and his client.

In the letter sent Wednesday, Cruz's attorney Chris Gober slams Goldman's "flimsy assertion" that the Texas senator's campaign knowingly mislead the public and questions his basis for legal action. Gober also cited Trump's statement during the eighth GOP debate that Planned Parenthood "does some wonderful things" as a reason he cannot be taken seriously as a committed pro-life candidate.

"Being pro-life and supporting Planned Parenthood are incompatible. Moreover, Trump has recently donated political contributions to many pro-choice candidates and officeholder, including Chuck Schumer, Andrew Cuomo, Anthony Weiner, and Rahm Emanuel," Gober wrote. "Mr. Trump also donated to the New York State Democratic Party, whose platform is pro-choice, and he has donated to pro-choice candidates as recently as 2014.

"Suffice it to say, there is ample evidence casting grave doubt about the truthfulness of Mr. Trump's campaign claims that he is truly pro-life," he added.

Furthermore, Gober introduced the 1964 Supreme Court case New York Times Co. v. Sullivan as legal precedent protecting the Cruz campaign from facing a legal battle over its latest ad. The court's ruling put the onus on public officials suing for defamation to prove statements against them were made with "actual malice," or intent to do harm.

"In conclusion, I would be remiss if I didn't explicitly state the obvious: The truth is an absolute defense to a defamation claim," Gober wrote. "Therefore, your client has no legal basis to demand that our campaign cease airing the ad, and your demand for "prompt written assurances" that we have pulled the spot will not be forthcoming."

He continued, "To the contrary, we not plan to air the ad with greater frequency."

Shortly after Cruz's press conference Wednesday, and his attorney's pledge to run the ad more often, Trump himself responded in a statement to the Washington Examiner.

"Ted Cruz has already had one of his ads pulled off the air concerning Senator [Marco] Rubio because it was totally false... he was forced to apologize to Dr. Ben Carson for fraudulently stealing his votes in Iowa, and was embarrassed by his phony voter violation form," Trump said. "He is a liar and these ads and statements made by Cruz are clearly desperate moves by a guy who is tanking in the polls."

"I am pro-life and I do not support tax payer funding for Planned Parenthood as long as they are performing abortions. I have been clear about my position on this issue for years," he added.

Trump also said that any lawsuit he brings against his opponent, whether in relation to Cruz's attack ad or his Canadian-birth status, would be "legitimate."

"If I want to bring a lawsuit it would be legitimate. Likewise, if I want to bring the lawsuit regarding Senator Cruz being a natural born Canadian I will do so," he said, adding, "Time will tell, Teddy."