US food company Kraft Heinz has made a bid for Unilever in what could be one of the biggest mergers in corporate history if it goes ahead.
Unilever, an Anglo-Dutch company, is one of the largest firms listed in Britain and owns well-known brands including Persil, Dove, Pot Noodle, PG Tips and Marmite.
The offer made by Kraft Heinz - behind brands like Heinz ketchup and Philadelphia cheese - was worth more than $143bn (£115bn).
Unilever has, however, rejected the initial offer, saying the terms of the approach "fundamentally undervalues" the company.
"Their proposal represents a premium of 18% to Unilever's share price as at the close of business on 16 February 2017," the firm said.
"This fundamentally undervalues Unilever.
"Unilever rejected the proposal as it sees no merit, either financial or strategic, for Unilever's shareholders.
"Unilever does not see the basis for any further discussions."
Some of the biggest mergers in history:
$172bn - Vodafone AirTouch for German conglomerate Mannesmann AG in 1999
$134bn - Budweiser maker Anheuser-Busch InBev for SABMiller in 2015
$130bn - Verizon Communications for Verizon Wireless in 2013
$112bn - AOL for Time Warner in 2000
But Kraft Heinz struck a more hopeful note, saying: "Kraft confirms that it has made a comprehensive proposal to Unilever about combining the two groups to create a leading consumer goods company with a mission of long-term growth and sustainable living.
"While Unilever has declined the proposal, we look forward to working to reach agreement on the terms of a transaction."
The firm warns, however, that agreeing a deal with Unilever is by no means assured.
Unite, the union representing many Unilever workers, urged Unilever to continue to resist the takeover attempt, saying any change in management would lead to "job losses and poorer products for customers".
Unite national officer Rhys McCarthy said: "Unite is seeking an urgent meeting with Unilever senior management where we will seek assurances that the company will resist this predatory takeover by Kraft Heinz.
"Unite members make household products which are much loved by UK consumers.
"Kraft Heinz and their backers' reputation for cost cutting, we believe, will lead to great brands being harmed through job cuts and a never ending drive to push costs down.
"This takeover bid is, we fear, driven by a desire for a growth in sales, not through product innovation and maintaining great brands, but by gobbling up a major competitor and slashing costs to generate a quick buck."
Kraft Heinz, which is listed on the US stock market, has an estimated value of £85bn while Unilever is thought to be worth around £101bn.
If the two companies were to agree a deal it could represent the biggest takeover of a British company ever seen.
Heinz purchased Kraft in 2015, creating the third largest food and drinks company in North America at the time and the fifth largest worldwide.
The firm is controlled by a partnership between a company run by American business magnate Warren Buffett, Berkshire Hathaway Inc, and Brazilian investment firm 3G Capital.
Shares in Unilever rose 11% on the news, while Kraft Heinz shares jumped by more than 8% on the opening of the US markets.
Unilever was recently involved in a dispute with Tesco due to attempts by the firm to raise wholesale prices by up to 10%, following the collapse in sterling after the Brexit vote.
(c) Sky News 2017: Kraft Heinz approaches Unilever in mega-merger deal