Wednesday's statement from Catherine Ashton says she is "concerned" by the conviction of Abdullah Abu Rahmeh. She says it aims to prevent Palestinians from protesting Israeli actions.
Abu Rahmeh, who led marches from the village of Bilin to the barrier, has been jailed since December. An Israeli military court convicted him Tuesday of incitement and demonstrating illegally.
Israeli Foreign Ministry spokesman Yigal Palmor said Ashton's "interference with a transparent legal procedure is highly improper."
Israel says the barrier is crucial to keep out attackers. Palestinians say it takes their land.