NEW YORK (AP) — New York City officials say the rising power of disparate militant groups around the world presents the most complex and layered terrorism danger since the twin towers were destroyed 13 years ago.

There is no immediate threat to New York ahead of the Sept. 11 anniversary this week. But police officials say New York remains the top target and that makes it much more critical to prepare for events, including the U.S. Open tennis tournament, the United Nations General Assembly and Thursday’s commemoration.

New York Police Commissioner William Bratton said the department is prepared.

That means thousands of officers in specialized teams, bomb-sniffing dogs, undercover officers and teams of police using radioactive detection devices and other high-tech tools. Intelligence officers around the globe also will be reporting in regularly.