 Upon learning of the strong Mexican resistance to his proposed modifications, Webster instructed Letcher to negotiate the most favorable terms to which the Mexicans would agree.On January 25, 1851, Letcher signed a second treaty that was slightly more favorable to the Americans.During the time it had taken both sides to negotiate the treaty, however, public sentiment in Mexico had turned decidedly against any form of treaty with the United States regarding Tehuantepec.