NEW YORK (Reuters) -The U.S. Securities and Exchange Commission (SEC) on Thursday urged a federal judge to force billionaire Elon Musk to testify for its investigation into his $44 billion takeover of social media giant Twitter, now known as X.

In a document filed in federal court in San Francisco on Thursday, the SEC defended its efforts to compel Musk's testimony, saying agency officials are acting within their authority.

The SEC last month said it was investigating Musk's 2022 purchases of stock in Twitter -- which Musk subsequently renamed X -- and his statements and SEC filings relating to his takeover of the social media giant. Musk had refused to attend a September interview for the probe, the SEC said.

Musk and his lawyers on Nov. 2 asked the judge to deny the SEC's motion to compel his testimony, saying Musk had already testified twice and that the agency was exceeding its authority.

But the SEC on Thursday rejected those claims, saying agency officials are indeed granted authority by law to seek testimony and documents as they pursue their investigative work.

The SEC has previously also noted that it has received new documents in the investigation since their last interview.

The court battle is the latest flare up in the acrimonious relationship between the U.S. market regulator and the world's richest person.

(Reporting by Chris Prentice; editing by Michelle Price)