WASHINGTON (CNN) -- Former U.S. Ambassador Joseph Wilson has filed a motion to quash the witness subpoena issued last week for his testimony for the defense in the Lewis "Scooter" Libby trial, arguing the defense has no right to call a witness whose testimony would not be helpful to the defense.

"Mr. Wilson is such a witness," the motion to quash said. "He personally observed none of the events that led to Mr. Libby's indictment and he has no direct personal information regarding Mr. Libby's defense, i.e., the matters Mr. Libby worked on at the White House or Mr. Libby's memory or veracity.

"Thus, Mr. Wilson's testimony would not be relevant or material to the defense and, therefore, should not be compelled."

Libby's trial on charges of perjury, obstruction of justice and making false statements to investigators probing the 2003 disclosure of CIA officer Valerie Plame's identity is scheduled to begin in mid-January. He resigned as Vice President Dick Cheney's chief of staff on the day he was indicted in October 2005.