“Bayer and Monsanto today announced that they signed a definitive merger agreement under which Bayer will acquire Monsanto for USD 128 per share in an all-cash transaction,” the firms said in a statement.

Bayer repeatedly increased its offer to Monsanto since its first $122-per-share bid, but the US firm had until now held out for more cash.

“This represents a major step forward for our crop science business,” Bayer chief executive Werner Baumann said in the statement.

The two firms said that the deal “brings together two different, but highly complementary” businesses.

Monsanto shareholders still have to approve the deal, as do regulators — with Bayer staking a $2 billion reverse antitrust break fee in case the merger is rejected by US or European authorities.

The deal is expected to be completed by the end of 2017.

Bayer has been pursuing Monsanto since late May, when it made an initial bid of $122 per share (109 euros), valuing the US genetically modified (GM) crop giant at $62 billion.

Monsanto rejected that bid, but said it was “open” to further talks.