U.S. President George W Bush has approved the deployment of 3,200 Marines to Afghanistan to meet a shortfall caused by the reluctance of NATO allies to send more troops to the war-torn country, DPA reported. Bush approved the recommendation by Defence Secretary Robert Gates, the Pentagon said Tuesday. Gates has been mulling sending more troops there ahead of a possible offensive by the Taliban on the southern part of the country. About 2,200 of the Americans will by placed under NATO's International Security Assistance Force command, while 1,000 will operate under US command to assist in the training of Afghan security forces, the Pentagon said. "The United States is doing its part to ensure ISAF has the forces necessary to ensure the hard-fought gains accumulated during the past six years by the Afghans and NATO are made irreversible," the Pentagon said. There are already 26,000 US soldiers in Afghanistan, about half of them under NATO command.