WASHINGTON, Oct 21 (Reuters) - The U.S. State Department has approved the potential sale of three weapons systems to Taiwan including missiles and artillery that could have a total value of $1.8 billion, the Pentagon said on Wednesday.

The formal notifications to Congress on Wednesday were for a truck-based rocket launcher made by Lockheed Martin Corp called a High Mobility Artillery Rocket System (HIMARS), long-range air-to-ground missiles made by Boeing Co called SLAM-ER, and external sensor pods for F-16 jets that allow the real-time transmission of imagery and data from the aircraft back to ground stations. (Reporting by Mike Stone and David Brunnstrom Editing by Chris Reese)