RBS Citizens Financial Group (RBS) in Providence, R.I., has signed a referral agreement with brokerage Oppenheimer & Co., in a bid to boost its commercial lending to middle-market businesses.

The deal helps RBS provide its existing customers with additional investment banking services from Oppenheimer, including financial advisory and equity capital markets services. In exchange, the brokerage is referring its own middle-market customers to RBS for commercial banking products and other services, including debt syndications and extensions of credit.

The two companies, which were slated to announce the referral agreement on Tuesday, say they are already referring customers to each other. Oppenheimer is a subsidiary of Oppenheimer Holdings Inc. (OPY)

Terms of the deal were not disclosed. 

Robert Matthews, head of RBS Citizens commercial banking, said in a press release that the bank's middle-market business customers are increasingly looking for help with mergers and other capital markets activities. 

"Combining our existing strengths with Oppenheimer enables us to provide RBS Citizens clients with the full breadth and depth of capabilities necessary to advise and finance these strategic objectives," he said.