One World Trade Center rises above the lower Manhattan skyline in this aerial photo, Tuesday, Aug. 30, 2011 in New York. Behind the tower are the Hudson River and New Jersey. Sept. 11, 2011 will mark the tenth anniversary of the terrorist attacks in the United States. (AP Photo/Mark Lennihan) The Associated PressWASHINGTON (AP) — The federal government is stepping up security around the country in preparation for the 10th anniversary of the 9/11 attacks and conducting confidential briefings with state and local law enforcement organizations. But officials say there is no specific indication that a terror plot against the U.S. is under way.An intelligence official tells The Associated Press that Americans can expect more security at airports, mass transit stations, U.S. borders, government buildings and major athletic events over the next month. The official spoke anonymously to discuss sensitive security matters.The FBI and Homeland Security Department have been briefing state and local law enforcement around the country on ways to enhance security and be aware of potential threats. Intelligence briefings are routine, but the recent focus has been on the 10-year anniversary.