WASHINGTON (Reuters) - U.S. Senate Majority Leader Harry Reid issued a strong defense on Thursday of Senator Dianne Feinstein, who heads the Senate Intelligence Committee, in a dispute in which the committee and the CIA each allege they were spied upon by the other.

Reid, in a letter to Attorney General Eric Holder, called the Central Intelligence Agency's access to the Senate panel's computer network a "serious breach" and "indefensible." He said he would begin a forensic examination of computers assigned for exclusive use by Senate Intelligence.

(Reporting by Richard Cowan and Patricia Zengerle; editing by Doina Chiacu)