Adds start of US trading

By Tom Polansek

CHICAGO, April 28 (Reuters) - U.S. wheat futures sank to contract lows on Monday on expectations that rain will benefit crops that have been struggling with dryness in the Plains region.

Corn and soybean futures were nearly unchanged.

Rain is projected to aid wheat crops in the Plains over the next 10 days, Commodity Weather Group said, adding that some parts of Texas and Oklahoma may receive six to eight inches.

The showers should benefit yields for the region's hard red winter wheat, which is used to make bread, said Rich Nelson, chief strategist for Allendale.

"We have the very heavy rains lined up directly ahead," he said.

The most actively traded wheat futures at the Chicago Board of Trade were down 13-3/4 cents at $5.31-1/4 per bushel by 11 a.m. CDT (1600 GMT). The contract set a low of $5.27-1/4 earlier in the session.

Most-active K.C. July hard red winter wheat futures KWN25 were down 10 cents at $5.41 a bushel, after earlier setting a contract low of $5.34-1/2.

The U.S. Department of Agriculture is slated to release updated condition ratings for U.S. winter wheat crops in a weekly report due at 3 p.m. CDT.

"For HRW right now, rain makes grain," CHS Hedging said in a note.

In other markets, most-active CBOT soybeans Sv1 were flat at $10.59-1/4 a bushel. Corn Cv1 slipped 1-1/2 cents to $4.84 a bushel.

Traders were assessing disruptions to U.S. agricultural exports from U.S. President Donald Trump's trade war with China, the world's biggest soybean importer.

News last week that China exempted some U.S. goods from its tariffs sparked hopes for a de-escalation. However, U.S. soybean and grain exports to China look like they will be stopped by Chinese tariffs for the foreseeable future, traders said.

They were waiting for the USDA to issue a weekly update on U.S. corn and soy planting progress later on Monday.

(Reporting by Tom Polansek in Chicago. Additional reporting by Michael Hogan in Hamburg and Naveen Thukral in Singapore; Editing by Marguerita Choy and Vijay Kishore)

((Thomas.Polansek@tr.com))