The United Stated is raising the alert level at its domestic military bases just days before the country marks the 10th anniversary of the September 11, 2001 attacks on New York and the Pentagon.

Pentagon spokesman George Little said the move was a precautionary measure and not the result of any particular threat.

Al-Qaida terrorists killed nearly 3,000 people when they hijacked four planes, crashing two of them into the World Trade Center in New York and one into the Pentagon, outside of Washington. A fourth plane crashed in a field in Shanksville, .

Also Wednesday, top U.S. lawmakers said the Department of Homeland Security has made the nation safer.

The chairman of the Senate Homeland Security and Governmental Affairs Committee said Wednesday the United States has been “spared another catastrophic terrorist attack” partly as a result of what the department has done. But Democratic Senator Joe Lieberman added the country has also been “just plain lucky.”

Lieberman and the committee's leading Republican, Senator Susan Collins, also expressed concerns about some of the agency's flaws, including problems with buying and using technology that did not work.

Lawmakers created DHS eight years ago to prevent a repeat of terrorist attacks. The new department combined 22 agencies and almost 200,000 employees under the leadership of a homeland security secretary.

A report released Wednesday but the U.S. Government Accountability Office praised the department for leading key initiatives to prevent terrorism. But it also said DHS needs to address ongoing management problems and spending issues.

DHS is the third largest U.S. government agency, with an annual budget of more than $50 billion.