Staples Inc. and Office Depot Inc. are in advanced talks to combine, the Wall Street Journal reported, following pressure on the companies from an activist investor.

The price of the proposed transaction couldn’t be learned and there’s no guarantee a deal will be reached, according to the newspaper, which cited people familiar with the matter. Staples has a market value of $11 billion, while Office Depot is worth $4.1 billion based on Monday’s closing price in New York.

Starboard Value, an investor with stakes in both retailers, last month sent a letter to Staples Chief Executive Officer Ronald Sargent demanding his company engage advisers to work on a deal. The combination could deliver more than $2 billion in cost savings and help the retailers compete with larger chains and online offerings, according to Starboard.

At the time, Staples gave a tepid response to Starboard, saying it had already met with the investment firm on several occasions to consider ideas. It didn’t discuss its willingness to make a deal.

Shares of both companies rose in European trading. Staples traded at the equivalent of $17.50 at 9:03 a.m. in Frankfurt, up 2.1 percent on the $17.14 closing price in New York. Office Depot rose 2.5 percent to the equivalent of $7.82.

Starboard pushed successfully for a merger of Office Depot and OfficeMax, a deal that happened in 2013, and investors have speculated that it could replicate that strategy with Staples. New York-based Starboard has said it owns about 6 percent of Staples and almost 10 percent of Office Depot.

Kirk Saville, a spokesman for Framingham, Massachusetts- based Staples, and Karen Denning, a spokeswoman for Boca Raton, Florida-based Office Depot, didn’t immediately respond to requests for comment outside of normal business hours following the WSJ report.