Mayor Bloomberg is backing plans to build a $1 billion sports stadium on Manhattan’s West Side to lure the Jets and the 2012 Olympics to New York City, his economic-development czar told The Post.

Only days after Bloomberg put new baseball parks on the back burner, Deputy Mayor Daniel Doctoroff revealed the mayor was “in sync” with the Olympic-bid committee’s plan to build a 75,000-seat stadium as part of an expansion of the Javits Convention Center.

“I certainly hope that in my new capacity, we will make the Javits expansion a high priority and look seriously at the far West Side,” Doctoroff said.

Doctoroff, who led New York’s 2012 Olympic bid before his appointment, indicated he received Bloomberg’s support for the ambitious plan before he was named deputy mayor for economic development.

“He [Bloomberg] wouldn’t have picked me, and I would not have accepted, if we were not in sync on this,” he said.

Under the Olympic-bid plan, construction work on the facility could start as early as 2005 and be ready for operation in 2009 – after the football Jets’ lease at Giants Stadium in the New Jersey Meadowlands expires.

The proposed 314,000-square-foot stadium would be built over the rail yards south of the Javits Center, between 29th and 34th streets and 11th and 12th avenues, according to plans outlined in Olympic and Jet documents.

It would feature a retractable roof, allowing it to be used for indoor conventions, as well as for staging the Olympics’ opening and closing ceremonies and athletic events and the Jets’ eight home games a year.

Jet owner Robert Wood “Woody” Johnson said last May he wanted to bring the team back to New York, and has indicated he would put at least $300 million into the West Side stadium project.

Doctoroff said the stadium would be “essentially a self-financing plan.”

“This again is really a Javits expansion which would be usable for football – the Jets would have to pay their fair share, and it is way too preliminary to talk about what that would be – but certainly, we have more flexibility than people might think,” he said.

Consultants and politicians have long agreed that the Javits – with only around 814,000 square feet of exhibition space – must double in size for New York to remain competitive with other American cities.

Gov. Pataki has been pushing for an expansion since he was elected, while Bloomberg, before he was elected mayor, said that he would consider the plan.

New York has been chosen as one of five U.S. finalists for the 2012 Olympics; the International Olympic Committee will decide the host city in 2005.