The United States is ramping up security level around the country Wednesday as the 10th anniversary of the 9/11 attacks approaches, with the White House saying the administration is taking "all necessary steps" to guard against possible terror plots coinciding with the anniversary.

White House Spokesman Jay Carney said during his Wednesday news briefing that President Barack Obama convened his homeland security team the previous day "to ensure that all necessary homeland security measures, cautions are been taken in advance of the upcoming tenth anniversary of 9/11."

The meeting wasn't announced on Tuesday, and participants were described as "all the senior people with responsibility in homeland security," including Obama's chief anti-terrorism advisor John Brennan, National Counterterrorism Center Director Matthew Olsen and Secretary of Homeland Security Janet Napolitano.

Carney said there's no specific, credible threat to the United States for the time being, but "this is a significant anniversary. Al-Qaeda and others have expressed interest in anniversaries in the past. So we remain ever vigilant through the anniversary and beyond."

Carney wouldn't reveal the specific decisions or discussions occurred during the meeting, saying this is one of "a series of meetings in the past four months," some chaired by Obama, while others run by Brennan.

These meetings "all work towards the anniversary to ensure that we are doing what we should be doing to safeguard the homeland," added Carney.

Earlier in the day, Pentagon spokesman George Little said Defense Secretary Leon Panetta has ordered increase of force protection level at military bases in the United States through Sept. 11. Carney said he was sure the measures taken by the Pentagon are "precautionary" in nature.