NYPD Commissioner Kelly: 'Terrorism is a theater and this is the world’s biggest stage’

Washington (CNN) - U.S. officials have "specific, credible but unconfirmed" information about a potential al Qaeda threat against the United States coinciding with the 10th anniversary of the September 11 terrorist attacks.

"We have received credible information very recently about a possible plot directed at the homeland that seems to be focused on New York and Washington, D.C.," a senior administration official told CNN Thursday.

New York City is already on higgh alert, with ceremonies set to take place at the World Trade Center cite this Sunday.

This morning on American Morning, Christine Romans talks with New York City Police Commissioner Ray Kelly, who says though there is an increased police presence in the city, it's up to citizens to be on alert as well.

"We have a big city and obviously it's an open city," Kelly says. "That's why we're a functioning and successful city. But we need the public's help. We need them to be vigilant."

See the entire interview here.