WASHINGTON, May 19 (Xinhua) -- A U.S. Navy warplane on counter-narcotics missions crossed into Venezuelan airspace Saturday night due to possible course error, the Associated Press reported Monday.

　　The S-3 Viking aircraft, based in Curacao, was on a training mission in international airspace near Los Roques Island, Venezuela, and experienced "intermittent navigational problems," an unidentified Pentagon official was quoted as saying.

　　U.S. Navy officials are investigating the incident to determine exactly what happened, the official said.

　　It was reported that Venezuela has demanded the U.S. ambassador to Venezuela to explain the violation of its airspace by a U.S. military plane.

　　The S-3 aircraft, originally used for anti-submarine warfare and maritime surveillance, are now used largely for counter-narcotics activities.

　　The U.S. and Venezuela have been exchanging verbal fire for years, with Washington accusing Venezuelan government led by President Hugo Chavez of destroying the country economically and politically. Chavez and his government always reject U.S. accusation.