As the city reflects 21 years after 9/11, NYPD commissioner Keechant Sewell stressed the importance of staying vigilant in the fight against terrorism.

"While we maintain the position that we will try to thwart every single threat and prevent any terror attack that comes in New York City's way, I think it's important to know that we have to make sure that every single day we are assessing the threats that come our way, we are reviewing the intelligence and we have boots on the ground ready to respond to that," Sewell told Rocco Vertuccio and Shannan Ferry Sunday morning on NY1.

Sewell noted, however, that she feels Manhattan is much safer from terrorism than it was 21 years ago, and that the department is ready "to answer anything that happens in New York City."

"[The city is] exponentially safer. We have a Lower Manhattan security initiative. We have a 24-hour, robust intelligence operation, and the eyes and ears of every law enforcement officer in New York City."

In her first 9/11 as commissioner of the NYPD, Sewell stressed the importance of returning to the World Trade every year and honoring the thousands of lives lost.

"It's important that we come back here year after year to read those names and hear those names," Sewell said. "And remember what happened that day so we can never forget."

Twenty-three NYPD members died in the line of duty responding to the Sept. 11 attacks on the World Trade Center, according to the city. Many more have since died of 9/11-related illnesses.