WASHINGTON (AP) – The Senate is set to take a closer look at a proposed $66 billion merger of American seed and weed-killer company Monsanto and German medicine and farm chemical maker Bayer.

The deal combines two of the six U.S. and European companies that dominate the agrochemical market, and would create a global agricultural and chemical giant with a broad array of products. Senate Judiciary Committee Chairman Charles Grassley of Iowa has said he’s concerned that the consolidation could hurt American farmers who are already worried about rising costs.

After months of negotiations, St. Louis-based Monsanto Co. last week accepted an offer from Leverkusen, Germany-based Bayer.

The Senate panel will hear from those two companies and others at a Tuesday hearing on consolidation and competition in the U.S. seed and agrochemical industry.