Multinational agricultural giant the Monsanto Company said Wednesday it end its efforts to take over rival Syngenta after the Swiss company rejected its latest offer.

Monsanto said it believes there is still a value to combining the companies, but without “constructive engagement” from Syngenta, the company has decided to move on and focus on standalone growth.

“Monsanto will continue to focus on its growth opportunities built on its existing core business to deliver the next wave of transformational solutions for agriculture,” the company said.

Syngenta rejected lower bids from Monsanto earlier this year. The proposed deal would have seen combined annual sales of more than $30 billion. In its most recent proposal, Monsanto increased its bid to 470 Swiss francs per share, or approximately $47 million, according to the Associated Press.

Syngenta said it rejected the latest proposal because it “significantly undervalued the company and was fraught with execution risk.”

Specifically, the company said Monsanto did not sufficiently clarity the following four issues:

-Their estimate of total cost and revenue synergies

-Their assumptions regarding net sales proceeds of seeds and traits

-The nature and extent of regulatory covenants that they were prepared to offer

 -The assessment of risks and benefits from a tax inversion to the United Kingdom