The New York police department said there was no indication that the attacks in Belgium were connected to New York, but ordered the steps as America's biggest city of 8.4 million began the morning commute.
"These teams have been deployed to crowded areas and transit locations around the city out of an abundance of caution to provide police presence and public reassurance as we closely follow the developing situation overseas," the police department said in a statement.
New York police also took a swipe at proposed federal spending cuts on counter-terrorism, calling them "irresponsible" in the city that "is widely recognized as the nation's top terror target."
At least 26 people were killed and dozens wounded in bombings at Brussels airport and a metro station in the city today that is home to the European Union and NATO.