German drugs and crop chemicals company Bayer has confirmed that it has closed a deal to buy US seeds firm Monsanto for $66 billion.
It ends months of wrangling after increasing its bid for a third time.
Reuters is quoting a source close to the deal who said an agreement had been signed for Bayer to pay $128 per share, up from its previous offer of $127.50 a share.
That would be the biggest takeover deal of the year so far and the largest cash bid on record.
Bayer and Monsanto were not immediately available to comment.
A deal would create a company commanding more than a quarter of the combined world market for seeds and pesticides in the fast-consolidating farm supplies industry.
However, competition authorities are likely to scrutinise the tie-up closely, and some of Bayer's own shareholders have been highly critical of a takeover plan which they say risks overpaying and neglecting the company's pharmaceutical business.
The transaction includes a break-fee of $2 billion that Bayer will pay to Monsanto should it fail to get regulatory clearance, the source told Reuters, adding the two firms expect the deal to close by the end of 2017.
Bayer shares were up around 2.5%; Monsanto's shares were down around 1% in pre-market trade.
Bayer's move to combine its crop chemicals business, the world's second largest after Syngenta AG, with Monsanto's industry leading seeds business, is the latest in a series of major tie-ups in the agrochemicals sector.
The German company is aiming to create a one-stop shop for seeds, crop chemicals and computer-aided services to farmers.
That was also the idea behind Monsanto's swoop on Syngenta last year, which the Swiss company fended off, only to agree later to a takeover by China's state-owned ChemChina.
Bayer and Monsanto were in talks to sound out ways to combine their businesses as early as March, which culminated in Bayer coming out with an initial $122 per-share takeover proposal in May.
Antitrust experts have said regulators will likely demand the sale of some soybeans, cotton and canola seed assets as a condition for approving the deal.
