US chemical companies DuPont and Dow Chemical Co have agreed to merge in a deal that would value the combined company at $130 billion US.

The plan is to eventually split into three separate companies focused on agriculture, materials and specialty products.

Shareholders of Dow and DuPont will each own about half of the new company, to be called DowDuPont.

The CEO of the new company will be DuPont Chief Executive Ed Breen, while Dow Chemical CEO Andrew Liveris will be executive chairman.

The deal is expected to face intense regulatory scrutiny.