The Commerce Department didn't disclose details of the emerging agreement, but it is likely to include tighter limits on the amounts and types of sugar products Mexicans can sell in the U.S.
But U.S. growers and the cane refining industry have said the agreement is not working because Mexico has been sending semi-refined sugar rather than the raw sugar that U.S. refiners need. Some of their Mexican counterparts also expressed anger at what they see as unfavorable terms.
The sources did not give details of the agreement, but one said it would benefit both countries.
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A fifth of the sugar that Mexico sold a year ago went to the US, with farming of the crop accounting for 2.4 million jobs across 15 states in Mexico.
U.S. Commerce Secretary Wilbur Ross came close to hammering out a compromise deal before an earlier deadline in May, but it fell through as the U.S. sugar lobby upped its pressure on U.S. lawmakers, said two sources familiar with the talks.
The Mexican official and a U.S. industry source said the USA sugar industry then came back with additional demands outside of the terms agreed on earlier.
The powerful lobby also includes Imperial Sugar Co, owned by Louis Dreyfus Co, and United States cane and beet growers.
Mexico once jealously guarded its oil and energy industries from US interference, but now USA legislators say they sense Mexico wants to include the energy sector in a re-negotiation of the North American Free Trade Accord. NAFTA opened the doors to Mexican sugar in 2008, which the US government determined was unfairly subsidized, driving down prices.