WHITE PLAINS, NY — County executives from Westchester, Rockland and Putnam have announced their support for the new Tappan Zee Bridge in the New York suburbs.

The leaders’ backing is essential. They sit on a council that must unanimously approve the suburban bridge to make it a federal project.

The county executives had previously expressed some doubts about the $5.2 billion bridge plan. It lacks a full-scale mass transit component.

But they said Thursday that Gov. Andrew Cuomo has agreed to the formation of a task force. It will make mass transit recommendations within a year.

Westchester County Executive Rob Astorino said that means mass transit will not be an afterthought.

Construction could start late this year or early next year.