As labor groups line up an effort to return the Independent Democratic Conference to the mainline conference, unions are backing the IDC’s leader, Bronx Sen. Jeff Klein.

On Friday, Klein unveiled yet another labor endorsement, this time for the Uniformed Fire Officers Association.

“The UFOA does not forget that when Mayor Bloomberg closed six engine companies in 2003, Jeff Klein led a legislative investigation that revealed the consequences of that dangerous reduction in the fire service. His dogged pursuit of the truth revealed a 10 second increase of response times city-wide,” Hagan said.

Klein faces Democratic former city councilman Oliver Koppell in a primary this fall.

Koppell has received the backing of the labor-supported Working Families Party, but Klein has received a number of labor endorsements as well as the backing of the Bronx political establishment.

Should Klein, the IDC and the mainline conference strike some sort of agreement before the primary, Koppell wouldn’t rule out leaving the race, he told Zack Fink of NY1.

“I think that that it is highly unlikely to happen. And will face that consequence or that situation if it happens. I’m not going to predict,” Koppell said.