The State Department noted al-Qaida and its affiliates "have demonstrated the intent and capability to carry out attacks against the United States and our interests around the world."
Defense spokesman Marine Col. Dave Lapan told Pentagon reporters Friday the department is "keenly aware" an attack is possible but no direct threat has been detected.
"There is no specific or credible intelligence that al-Qaida or its affiliates are plotting attacks in the United States to coincide with the 10-year anniversary of 9/11," Homeland Security Secretary Janet Napolitano said in a statement.
Lapan noted after the May assassination of Osama bin Laden in Pakistan, there was evidence al-Qaida was developing plans to mark the anniversary but to date, no specific plans have been uncovered.
"We will obviously be ... watching closely [and maintaining] increased vigilance," Lapan said. "We may take additional security steps based on information."