Punch Taverns, the UK's biggest pub firm, has confirmed a merger proposal for rival chain Mitchells & Butlers.
M&B owns the All Bar One and Harvester chains
The all-share offer would see Mitchells & Butlers shareholders own 50% of the enlarged company, and also receive a cash sweetener of £175m.
But Punch said it was an initial plan and there was "no certainty that any offer will ultimately be made".
Mitchells & Butlers, which owns the Harvester chain, is vulnerable after a failed property deal cost it £274m.
Shares in Mitchells rose more than 5% to 473.2 pence, while Punch shares fell 2.6% to 695p.
Up for sale
Punch said there "was substantial strategic rationale" in combining the two businesses, "including opportunities for operational synergies in the managed pub business and through a reduction in central costs".
M&B said it would consider the proposals put forward by Punch along with others.
M&B, which also owns the All Bar One chain, effectively put itself up for sale last week, after plans to sell most of its pubs to a debt-financed joint-venture with property tycoon Robert Tchenguiz fell through.
Analysts said the deal could face obstruction from Mitchells' shareholders.
"This is confirmation of a long standing suggestion - pretty sensible, deliverable and quick - but does not offer what M&B's shareholders most want - namely a profitable exit," said Blue Oar analyst Mark Brumby.
M&B's weakened financial position has said to have attracted a lot of interest, including from private equity groups Blackstone, Cinven, TPG and CVC.
M&B's largest shareholder, Mr Tchenguiz, may also launch a bid for the firm.
He currently has a 23% stake.
A merger of Punch and M&B would create a pub giant worth around £3.7bn, with more than 10,500 outlets.