Oil and gas giant Shell is in discussion to acquire its rival energy firm BP in what could turn out to be one of the largest M&A deals ever, a report by The Wall Street Journal said on June 25.

Both the British oil majors are in active talks with each other and BP is “considering the approach carefully”, WSJ said. The deal will put Shell in a solid position compared to its bigger rivals Exxon Mobil and Chevron, the report said.

Shares of BP traded in New York rose as much as 10 percent to $32.94.

However, any sort of agreement is not certain yet between two of the biggest oil companies that control some of the most important energy sources, the report added.

BP is currently valued at $80 billion and a deal with Shell could take it past the $83 billion merger that created Exxon Mobil, WSJ said. Shell has a market value of over $200 billion and its stock has outperformed BP in the last few years, the report said.

BP is under intense pressure after years of under-performance and the intervention of aggressive activist shareholder Elliott Investment Management. Speculation has been growing that the London-based company would become a takeover target, and Bloomberg reported in May that Shell had been studying the merits of a deal.

A successful combination of Shell and BP would become one of the oil industry’s largest-ever takeovers, bringing together the iconic British majors in a transaction that’s been discussed on and off for decades. The companies were once close rivals — with a similar size, reach and global clout — but their paths have diverged in recent years after BP moved too quickly into low-carbon energy.

With Bloomberg inputs