The city’s over-budget and problem-plagued 911 back-up call center is getting cut down to size.

Officials disclosed yesterday that they’re shaving at least $100 million from the $550 million estimated construction cost of a second 911 center off the Hutchinson Parkway in The Bronx that was supposed to break ground back in July 2009 and be completed in 2013.

Construction of a new backup center — which will be roughly half the size of the original proposal, has not yet begun. The overall tab for upgrading 911 is now estimated at $2 billion, up from the original $1.3 billion.