Bayer originally offered $122 per share but will up the offer verbally on July 1 after it "comprehensively addressed Monsanto's questions concerning financing of the transaction," the statement said.
"Bayer has offered a $1.5 billion reverse antitrust break fee, reaffirming its confidence in a successful closing," the company said in a statement.
The German chemical and pharmaceutical company also addressed concerns over regulatory matters and is prepared, if necessary, to make certain commitments to regulators to complete the proposed acquisition, Bayer said.
"We are convinced that this transaction is the best opportunity available to provide Monsanto shareholders with highly attractive, immediate and certain value," Werner Baumann, CEO of Bayer AG said in the statement. "Bayer is fully committed to pursuing this transaction."
The revised offer represents 40 percent premium over Monsanto's closing share price on May 9, the company said.
Monsanto acknowledged that it received a revised, non-binding proposal from Bayer.
"The Board of Directors of Monsanto will review the proposal, in consultation with its financial and legal advisors," Monsanto said in a statement.
Monsanto said it will have no further comment until the review is complete, and there is "no assurance that a transaction will be entered into or consummated."