(Sharecast News) - US paper giant International Paper is reportedly closing in on a formal £5bn-plus bid for London-listed packaging group DS Smith.

According to Sky News, 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 told Sky 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 also said it expects the combination of the companies to generate £375m of cost synergies.