The MTA is committed to a December opening of the Second Avenue Subway despite a new batch of concerns outlined in an independent engineer’s July report.

After more construction setbacks in June, there’s a “significant risk” that the long-delayed Second Avenue subway won’t be ready for its December opening, according to independent engineer Kent Haggas.

In part due to delays of the installation of communication systems, the MTA has had to push back its train testing on new tracks by one month, from Sept. 1 to Oct. 1.

Elevators for the 72nd Street station are also running behind schedule.

“We find that the project is not on schedule and has fallen further behind schedule in the month since our last report in June,” Haggas said at a Monday committee meeting. “We feel the project team now needs to implement and maintain a revised schedule for the completion of the testing program and for meeting [a December opening].”

The MTA remains steadfast in the face of the news. Contractors will be working overtime in order to open the first phase of the subway in December. Testing schedules have been accelerated.

“We are still projecting that the Second Avenue Subway will open in December,” said MTA spokeswoman Beth DeFalco.

The agency said the 72nd Street station remains the biggest threat to completing the project. To combat potential further delays, Judlau Contracting has ordered extra elevator cabs.

But to put the construction into perspective, the agency said that 96% of the station had been completed by July.

The first phase of the massive, $4.5 billion subway line will bring three new subway stations from 63rd Street to 96th Street as an extension of the Q line.