Donald Trump's former lawyer and self-described fixer Michael Cohen is delaying his testimony, which was scheduled to begin as early as Tuesday, in the former president's ongoing civil fraud trial in a New York state court.

"Unfortunately, I need to attend to a pre-existing medical condition that impedes my ability to testify this upcoming week," Cohen said in a statement on X on Friday.

He added that he still plans to testify "at the earliest opportunity."

"I look forward to testifying and correcting the record as to the multiple misstatements and responses by previous witnesses who stated … I don't recall. Unfortunately for them, I do," Cohen told ABC News Saturday.

Trump is still expected to attend the trial in person next week, according to sources familiar with his plans.

Cohen's delay was first reported by The Daily Beast.

Trump, his sons Eric and Don Jr., and Trump Organization executives are accused by New York Attorney General Letitia James of engaging in a decade-long scheme in which they used "numerous acts of fraud and misrepresentation" to inflate Trump's net worth in order get more favorable loan terms.

A lawyer for the New York Attorney General previewed Cohen's testimony in the state's opening statement as key evidence of a conspiracy within the Trump Organization to inflate the former president's net worth.

"Mr. Trump would call Allen [Weisselberg] and I into the office … He wanted to be higher on the Forbes list, and he then said 'I'm actually not worth $6 billion. I'm worth seven. In fact, I think it's actually now worth eight with everything that's going on,'" Cohen said in a portion of his deposition that was played during the state's opening statement. "Alan and I were tasked with taking the assets, increasing each of those asset classes, in order to accommodate that $8 billion number."

The former president has denied all wrongdoing and his attorneys have argued that Trump's alleged inflated valuations were a product of his business skill.

Cohen wrote about his ongoing medical issues in his book "Revenge," describing multiple pulmonary embolisms as a result of deep vein thrombosis as well as high blood pressure, which he said worsened during his 13-month prison sentence.

"I don't get cold feet. No one has stood up for truth to power more than me. I have a pre-existing medical issue that unfortunately needs to be attended to," Cohen said on X defending the delay.

ABC News' Eric Avram contributed to this report.