The United States will not be able to meet a request to send more troops to Afghanistan from NATO's top commander there until next spring at the earliest, U.S. Defense Secretary Robert Gates said on Tuesday. “Without changing deployment patterns, without changing length of tours, we do not have the forces to send three additional brigade combat teams to Afghanistan at this point,” Gates told the Senate Armed Services Committee. “My view is that those forces will become available probably during the spring and summer of 2009,” he said. President George W. Bush announced this month that the United States will deploy a Marine force of nearly 2,000 troops in November and an Army brigade of around 4,000 troops in January. U.S. Army General David McKiernan, the head of the NATO-led force in Afghanistan, said last week that he needed three more brigades as well as support units, totaling around 15,000 troops – in addition to those scheduled to arrive in coming months. The United States now has about 33,000 troops in Afghanistan, including 13,000 under NATO command.