General Motors will upgrade its Polish factory to produce the next generation Astra II model, raising the plant's exports by about $US200 million a year to $600 million, a GM spokesman told Reuters on Tuesday. Przemyslaw Byszewski told the news agency the carmaker would invest an unspecified amount within an "offset" investment package organised as part of Lockheed Martin's $3.5 billion sale of fighter planes to Poland's air force.