FILE PHOTO: The Opel development centre is pictured in Ruesselsheim, Germany July 5, 2018. REUTERS/Ralph Orlowski/File Photo

BERLIN (Reuters) - Carmaker Opel, a unit of France's PSA Group PEUP.PA, plans to slow production at two German sites after the summer to help cut costs in response to declining sales, regional newspaper Allgemeine Zeitung reported on Friday.

The company will cut production from 55 to 42 vehicles per hour at its Ruesselsheim plant and from 37 to 30 vehicles in Eisenach, the newspaper said, adding that output at Opel’s Polish site of Gliwice had already been slowed to 25 from 40 cars per hour.

In July PSA reported that it had succeeded in bringing the Opel-Vauxhall business back into the black after two decades of losses.

PSA bought the loss-making manufacturer and its British sister brand Vauxhall from GM last year in a $2.6 billion deal, and said it aimed to restore Opel to profitability by 2020.

Opel declined to comment on the details of the internal planning.

“Of course, we regularly adjust production planning in our plants,” Opel spokeswoman said.

The production throttling is sparking concern in the workforce that fewer cars could be built in the long term, the newspaper reported. But the management said the works council has agreed on its future plans for all European locations.

Early last month, the management reached an agreement with workers on investments in German sites and job protection measures until July 2023.