Sky News has learnt that International Paper and its advisers are hoping to reach an agreement on a recommended offer by the end of this week.

That would represent a key milestone in an unfolding takeover battle for one of Britain's biggest industrial companies, ahead of a deadline imposed by the City's Takeover Panel of 23 April.

City sources said on Monday that both International Paper and DS Smith were working towards a so-called Rule 2.7 announcement before this weekend, although they acknowledged that it could slip into next week, depending upon the progress of talks.

A recommended offer from the US-based predator would still leave the door ajar for Mondi, DS Smith's London-listed rival, to trump the International Paper bid.

Both prospective bidders have proposed all-stock deals, triggering a bidding war for a business viewed for years as a perennial takeover candidate.

International Paper said last week that it would pursue a secondary listing of its shares in London if it succeeded in its bid for DS Smith.

It added that it estimated the combination of the companies would generate £375m of cost synergies.

The interest in DS Smith, whose long-serving chief executive, Miles Roberts, recently announced plans to retire, comes amid a wave of industry consolidation.

DS Smith and International Paper both declined to comment.