Monsanto said it still believed in the value of a combination of the two agricultural seed and chemical giants, but will focus on building its core business and meeting long-term growth objectives.
Monsanto confirmed that it made a revised offer to Syngenta on Aug. 18, raising a previous offer to 470 Swiss francs, a value of roughly $47 billion. It also confirmed it raised a reverse break-up fee offer to $3 billion.
But, Monsanto said in a statement, Syngenta continued to spurn the overtures.
"Without a basis for constructive engagement from Syngenta, Monsanto will continue to focus on its growth opportunities built on its existing core business..." the company said in a statement.
Syngenta shares in Switzerland closed more than 18 percent lower on the news that the deal was off the cards.