Wheat rose for a fourth consecutive session on expectations of strong demand for US supplies as exporters in the Black Sea region run out of surplus stocks.
The most-active soybean contract on the Chicago Board Of Trade was down 0.1 percent at $9.19-1/4 a bushel by 0346 GMT, after three straight sessions of gains. Wheat added 0.1 percent to $5.27-3/4 a bushel and corn was down 0.1 percent at $3.80-1/4 a bushel.
Brazil's soy harvest in the second-largest producing state of Paraná is well ahead of last season, with limited damage to the fields from a drought in December, state agricultural research body Deral said on Tuesday.
One-quarter of the 2018/19 soybean area has been harvested in Paraná, according to Deral. At the same time last year, no soybean crop had been harvested in the state because of poor weather early in the crop season that had delayed planting and rains in January that further held up the harvest.
The US Department of Agriculture on Tuesday said that China bought 2.603 million tonnes of soybeans, the second confirmed sale since the world's top buyer of the oilseed announced last week it would buy 5 million tonnes of US supplies during trade negotiations between the two countries.
Traders are hopeful that progress is possible in talks to end the US-China trade war, which has hugely cut US soybean exports to China.
The wheat market is being underpinned by higher demand for US cargoes.
"We think the market has further modest gains a little further ahead," said Tobin Gorey, director of agricultural strategy, Commonwealth Bank of Australia, referring to US wheat futures.
"The market though will need to accumulate some proof that exports are running down US inventories before that can happen. We are guessing they will get that proof."
Traders are squaring positions ahead of the announcement of a backlog of crop reports from the USDA on Friday that were delayed by the partial US government shutdown.
The USDA data will include wheat sowings, US and South American corn and soybean production, US grain stocks and world crop season ending stocks.