Shares in Dow Chemicals and DuPont jumped following reports that the two companies are to merge, in a deal which could create a new agricultural chemicals giant.
The companies are said to be discussing a plan that would see the merged company spun out into three specialised subsidiaries, including a standalone agri-chemical company.
The news is the latest in a series of merger and takeover rumours that have been circulating in the agrichemicals sector.
CNBC reported that the merger could deliver cost savings of $3bn to the combined companies, citing industry sources close to the deal.
But the size of the merged company would require regulatory approval in a number of their operating regions, including the US, where it could run afoul of anti-trust legislation.
Dow's chief executive Andrew Liveris and DuPont chief executive Edward Breen would take the two top jobs in the new company, Reuters reported sources saying.
Mr Breen, who took over DuPont in October, has a previous record of ownership restructuring, after a stint at the conglomerate Tyco.
Breen spun Tyco out into six separately owned companies.
The agricultural input sector has been hit by squeezed farmer incomes around the world.
And US companies have also had to contend with a strengthening dollar, which weighs on their exports and overseas receipts.
Low returns in the sector, and ideas of large cost-savings to be gained by consolidation, have sparked widespread discussion of mergers and sales.
In August, the world's largest seed company, Monsanto, abandoned a $45bn bid for rival Syngenta.
The failure of those discussion sparked a feeding frenzy in the sector.
"Everyone is talking to everyone," the boss of Dow told investors in November.
As well as the Monsanto offer, the third such bid this year, Syngenta has already rejected a $42bn offer from the Chinese state-owned China National Chemical Corp.
In November the Monsanto executives told investors the company still had its eye on Syngenta, and expressed confidence that the sector would see major shakeups over the coming months.
Last week Dow sold off one of its line of herbicides to Gowan Company, including a number of chemical trademarks and a production facility in Canada, for an undisclosed sum.
Last month Dow Chemicals was reported to be in discussion with DuPont over the sale of Dow's ag-chemicals division.
And the Wall Street Journal has carried reports that Syngenta was in takeover discussions with DuPont as well.
Shares in DuPont were up 12.8% at $75.11 in midday deal in New York, while shares in Dow Chemical rose 11.3% to $56.665.
By William Clarke