U.S. soybeans were mostly unchanged on Tuesday and held near their lowest in almost a month as crop-friendly rains across Argentina continued to cap prices.

Corn extending losses into a fifth session on South American bumper crop expectations, while wheat was unchanged. Chicago Board Of Trade front-month soybeans were unchanged at $8.62-1/2 a bushel, not far from a low of $8.61-1/2 hit in the previous session - the weakest since Jan. 12. Soybeans closed down 0.6 percent on Monday.

Traders and analysts said the market remained under pressure from rains across Argentina.

"Argentina got the rainfall that forecasters expected over the weekend and on Monday. Consequently soybean crops are now looking just fine in both Argentina and Brazil," said Tobin Gorey, director of agricultural strategy, Commonwealth Bank of Australia.

Storms brought moisture to dry fields in Argentina during a key time for crop development. The country is the world's top exporter of soyoil and soymeal, and the No. 3 soybeans supplier.

Front-month corn fell 0.1 percent to $3.62 a bushel. In the previous session, it ended down about 1 percent after falling to a three-week low of $3.61-1/2 a bushel.

Traders said corn was under pressure from improved production prospects from South America. Front-month wheat was nearly unchanged at $4.58-1/4 a bushel. It closed down 1.8 percent on Monday after touching a one-month low of $4.57-1/2.

Market participants are now eyeing a U.S. Department of Agriculture (USDA) report scheduled for release later in the day for more trading cues.

Analysts expect the USDA in its monthly supply outlook to lift its estimates for U.S. grain supplies, but cut them slightly for world stocks from its last estimate.