* PSA considering options for Opel R&D ops
* Works council chief says difficult to agree deal
* Says will nonetheless sign labour pact this week (Adds further comments by works council chief, background)
By Arno Schuetze
RUESSELSHEIM, Germany, July 5 (Reuters) - Opel's management will face fierce resistance from its workers to a possible sale of the German carmaker's research and development arm, its top labour boss said on Thursday.
U.S. automaker General Motors sold loss-making Opel and its British sister brand Vauxhall to France's Groupe PSA in a $2.6 billion deal last year.
PSA is now looking to sell some of Opel's R&D operations as part of its effort to restore profitability at Opel by 2020 for the first time in two decades, French newspaper Le Monde reported on Tuesday.
"This won't go through without resistance. We believe a sale would threaten Opel's existence," Opel works council chief Wolfgang Schaefer-Klug told journalists following a staff meeting at the carmaker's headquarters in Ruesselsheim.
"It will be difficult to reach an agreement (on a sale). There is great concern that not much will be left of Opel (after a sale of the R&D ops)," Schaefer-Klug said.
Nonetheless, Opel's workers would not sabotage a labour agreement struck in May that offers wage concessions in exchange for investments in its German plants, which is expected to be signed on Friday, he added.
PSA and Opel have sounded out automobile engineering firms over the last few months on offers for four sections of the R&D business which is valued at about 500 million euros ($584 million), Le Monde reported.
Opel said on Wednesday that no decision had been made but that it was looking at options for the R&D arm considering the workload from GM would drop over the coming years.
Le Monde said French firms Altran, Akka and Segula and Germany's Bertrandt had been approached.
Citing an internal document from mid-May, Le Monde said the sale would cover Vehicle Engineering, Propulsion Engineering, Tool & Die Operations and the test centre.
The sections employ about 3,980 people, including at Opel's historic headquarters.
According to the document, the sale could come by the end of the year, which Schaefer-Klug said was unlikely to happen as labour representatives would need to be consulted first. ($1 = 0.8559 euros) (Reporting by Arno Schuetze; writing by Maria Sheahan; editing by Victoria Bryan/Jason Neely/Alexander Smith)