Switzerland's Syngenta rejected a second takeover proposal from agrochemicals firm Monsanto on Monday, saying its U.S. rival had made no attempt to seriously address regulatory concerns over the potential deal.
Monsanto, the world's largest seed company, faces mounting threats from both regulatory scrutiny and consumer opposition. A drive by the producer of Roundup herbicide to diversify its business is making Syngenta a compelling target, analysts say.
If Monsanto takes over Syngenta, it would gain a broad portfolio of fungicides, insecticides and other herbicides.
Monsanto offered on Sunday to pay a $2-billion reverse break-up fee to Syngenta if it cannot obtain global regulatory approvals for an acquisition.
Read MoreSyngenta rejects $45billion Monsanto takeover offer
"Monsanto's second letter represents the same inadequate price, same inadequate regulatory undertakings to close, same regulatory risks and same issues associated with dual headquarters' moves," Syngenta said in a statement.
"The only change by Monsanto is to add a wholly inadequate reverse regulatory break fee."
Syngenta had earlier rejected a $45 billion offer, but St. Louis-based Monsanto has continued to pursue a deal.