A U.S.- and Israeli-trained force of Libyan dissidents is fighting in the western Sudan as part of efforts to overthrow Col. Moammar Gadhafi, a newsletter reports.

Pentagon spokesman Fred Hoffman declined comment on the report by the London-based publication Africa Confidential. Another ranking U.S. defense official, who requested anonymity, denied the Defense Department was involved with any such Libyan dissident group."We can't speak for the CIA, but (the Defense Department) isn't in this," the source insisted.

The newsletter said the "substantial Contra force of Libyans" has been trained in Chad, Cameroon, Gabon, the Central African Republic and the United States.

The newsletter on African affairs, published every two weeks, gave no attribution for the detailed report, which was printed before U.S. F-14 fighters shot down two Libyan MiG-23s over the Mediterranean on Wednesday.

"The operation is well-advanced and is already putting pressure on Libyan and pro-Tripoli groups operating out of Sudan's lawless western region of Darfur," where fighting has broken out in recent days, it said.

The report did not detail how the force planned to overthrow Gadhafi but said it was operating under the emblem of the National Front for the Salvation of Libya, which is committed to ousting the Libyan leader.

Led by Col. Abdoulgassim Khalifa Haftar, the front's main force is based at Ouadi-Doum in northern Chad, it said.

The force has millions of dollars in Libyan equipment captured by the Chadian army and controlled by the U.S. Central Intelligence Agency, the newsletter said.

Up to 2,000 Libyan prisoners of war taken by the Chadians form the backbone of the force, with Western mercenaries being recruited in Kinshasa, Zaire, the newsletter said.

Its military activity, the newsletter said, is likely to be directed at the Libyan base at Tanoa south of the Aozou border strip, which Libya claims from Chad, and at pro-Libyan groups and Libyan troops in Darfur, Sudan.

The instructors include 30 Americans who arrived in Chad in 1987 and 49 Chadian soldiers under Capt. Ahmed Gourou who returned in December from a seven-month course at Camp Hall in Leadville, Colo., where they learned to decode information from U.S. radar and surveillance aircraft, it said.

American personnel are also in control of a major new supply base at Yoko in central Cameroon, the newsletter said.

In Cameroon, the Israelis trained 13 National Front members at Djoum under the authority of Col. Titus Ebogo, commandant of the presidential guard, it said, noting that Cameroon is Israel's main base in the region.

The Israelis are also training the guerrillas near Kaele in Cameroon and at Ndele in the Central African Republic, the newsletter said.