Reuters news agency says Dow Chemical Co. and DuPont are discussing a merger followed by a breakup into specialty units. One would be for agriculture pesticides and seeds.
The companies have combined stock-market value of more than $120 billion.
The companies declined comment.
Reuters says it has learned that the breakup would be material sciences, specialty products and agrochemicals.
This rumour follows hard on the heels of an attempted Monsanto takeover of Syngenta, a deal that some speculate might be revived.