* Chicago wheat pressured down by ample global supplies

* Market monitors Plains rain relief, Black Sea grain talks

* Traders anticipating U.S. export data

MEXICO CITY, April 26 (Reuters) - Chicago grains and soybean futures closed lower to mixed on Wednesday, as traders eyed sluggish demand and upcoming U.S. export sales data.

Wheat fell on news of ample short-term global supplies, despite the risk that an agreement allowing exports from war-torn Ukraine may end next month. Canadian farmers intend to plant 27 million acres (10.9 million hectares) of wheat, the most in 22 years, a government report said.

Soft wheat exports from the European Union in the 2022/23 season that started in July had reached 25.02 million tonnes by April 22, compared with 22.81 million a year earlier, data showed.

Corn and nearby soybean futures fell on the day, as traders monitored U.S. planting progress and cheap Brazilian export competition. Deferred soybean futures firmed.

Some corn traders said they would be watching U.S. Department of Agriculture's (USDA) weekly export sales report on Thursday for trade news.

"Based off of the weaker demand, we've kind of done enough and the markets are taking a breather," said Jack Scoville, market analyst at The Price Futures Group.

The most-active wheat contract on the Chicago Board of Trade (CBOT) dropped 11 cents to settle at $6.43 a bushel.

CBOT corn settled down 6-3/4 cents at $6.01 a bushel and soybeans closed 2-3/4 cents lower at $14.14-3/4 a bushel.

Wheat also has been pressured by rain forecast in much of the U.S. Plains this week and next. The moisture could help drought-affected hard red winter crops, though it may be too late to significantly improve yield prospects.

The improving U.S. weather and large Russian export supplies have encouraged investors to look beyond the risk that Moscow may quit the Black Sea corridor deal by May 18.

Russia's envoy to the United Nations in Geneva reiterated on Wednesday Moscow's position that no real progress had been achieved in addressing Russian concerns. (Reporting by Cassandra Garrison in Mexico City, Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Marguerita Choy)