MOSCOW (AP) _ The launch of an American communications satellite aboard a Russian booster rocket has been postponed because of problems with the satellite's transmission system, according to a news report Tuesday.

The Telstar-6 satellite has been sent back to the United States, the ITAR-Tass news agency reported, citing the Khrunichev space company. The Space Systems Loral company, which built the satellite, has detected a malfunction in its transmission system, the report said. The U.S. firm is a subsidiary of Loral Space and Communications Ltd. of New York.

The satellite was to be carried into orbit on Wednesday by a Proton booster blasting off the Baikonur cosmodrome, which Russia rents from the Central Asian nation of Kazakstan.

This is the fifth time this year that the Khrunichev company _ which manufactures the Proton _ had to postpone a launch because of satellite malfunctions, the report said.

Last month, the launch of an American Telesat Communications satellite was delayed for at least a year and the satellite returned to the United States.