The deal - which faces major anti-trust hurdles and must be approved by shareholders - will send shock waves through the industry by creating far and away the world's biggest agribusiness, with pro-forma 1998 sales of $7.9 billion.

The merged company, Syngenta AG, would rank first in agricultural chemicals and third in seeds, a release said. Astra Zeneca shares opened four per cent higher on the news at 105 pence, while Novartis - which has advanced strongly on speculation - added one per cent to open at 2,525 Swiss francs.