Top aides to President Obama on Sunday signaled that some U.S. troops could start coming home from Afghanistan as soon as July 2011, but most would likely remain there for several years. In appearances on all the major talk shows, Cabinet officials and military advisers clarified the president's position after he walked a political tightrope by announcing he will send 30,000 more troops to Afghanistan and that some will start coming home in 19 months. National Security Adviser Gen. James Jones told CNN's State of the Union that the July 2011 start of withdrawal was not a cliff, it's a ramp for beginning to turn over security responsibility to Afghan forces. Noting the U.S. strategic interests in the region, including nuclear power Pakistan next door, Jones said: We 're going to be in the region for a long time. Gen. David Petraeus, the head of U.S. Central Command, said on FOX News Sunday that Obama's strategy does n't trigger a rush to the exits, while Defense Secretary Robert Gates told CBS Face the Nation that there is n't a deadline. What we have is a specific date on which we will begin transferring responsibility for security district by district, province by province in Afghanistan to the Afghans, Gates said. The challenge has been to meet the need cited by military leaders for more troops and resources to wipe out terrorist networks in Afghanistan and to help the