Aug. 29 (Bloomberg) -- New York Times Co. Chairman Arthur Sulzberger Jr. must testify in a libel case against one of the newspaper's reporters that was brought by developer Donald Trump, a judge ruled.

Trump, 62, sued Timothy O'Brien and Time Warner Book Group Inc., now part of Paris-based Lagardere SCA, France's largest publisher, in January 2006 in state court in Camden, New Jersey, alleging libel for misrepresenting his net worth in the book ``TrumpNation: The Art of Being the Donald.''

Sulzberger must give sworn testimony at a deposition about a Sept. 6, 2005, e-mail exchange with O'Brien and details of a lunch meeting with O'Brien and Trump, New York Supreme Court Judge Joan A. Madden said in an Aug. 20 ruling.

``The balance of the testimony sought from Sulzberger alone is directed at his e-mail correspondence'' when ``O'Brien wrote that parts of the book would make Trump `go ballistic,''' Madden wrote.

Trump lawyers won permission in December from New Jersey Superior Court Judge Michael Kassel to take the deposition. Sulzberger fought a subpoena issued in New York, where the Times is based.

Diane McNulty, a spokeswoman for the Times, didn't return calls for comment on the judge's ruling yesterday.

``We intend to proceed vigorously and expeditiously'' with the deposition and trial, a Trump lawyer, William M. Tambussi, said in a statement yesterday.

Subpoena Quashed

Kassel also had ordered Times Executive Editor Bill Keller to testify about conversations with O'Brien about the 2006 book. Madden quashed the subpoena for Keller, saying his testimony wouldn't be related to the key issue of ``actual malice.''

Trump is seeking at least $2.5 billion in damages from O'Brien and Warner, contending O'Brien wrote that Trump, who doesn't disclose his finances, was worth from $150 million to $250 million, according to court filings.

Trump claims the figure is wrong and the book has cost him business deals by damaging his reputation.

The case is Trump v. O'Brien, Time Warner Book Group, L545-06, New Jersey Superior Court (Camden).

To contact the reporters on this story: Jef Feeley in Wilmington, Delaware at jfeeley@bloomberg.net; Phil Milford in Wilmington at pmilford@bloomberg.net.

Last Updated: August 29, 2008 00:01 EDT