DETROIT — General Motors Corp. is expected to cut several thousand salaried jobs and further slash truck production in response to falling U.S. sales and Wall Street's demands for more action to stem its losses, according to people briefed on the plan. GM Chairman and CEO Rick Wagoner is scheduled to discuss the changes at a news conference Tuesday morning. GM released no further details, but salaried job cuts and cuts to benefits and executive compensation are likely. The people briefed on the plan said GM will further reduce its truck production to focus more on small cars, and also will likely detail plans to raise more cash to fund its restructuring. The people requested anonymity because the plan was not yet public.