CHICAGO - U.S. wheat and corn futures weakened on Friday as traders monitored diplomatic talks aimed at resuming shipments of Ukrainian grain stalled since Russia's invasion, analysts said.

Soybean futures also declined as market participants booked profits before the weekend, brokers said.

Ukraine was in focus as the United Nations said its aid chief Martin Griffiths was in Moscow this week to discuss clearing the way for exports of grain and other food from Black Sea ports.

Russian President Vladimir Putin denied Moscow was preventing Ukrainian ports from exporting crops, though Russia's army has seized much of Ukraine's southern coastline and its warships control access to the country's Black Sea ports.

Sovecon, a leading agriculture consultancy in Moscow, raised its forecast for Russia's wheat exports in the new July-June marketing season to a record.

However, a resumption of Ukrainian sea trade is seen as crucial for grain markets, particularly after India last month decided to ban most wheat exports. Ukraine was the world's fourth-largest corn exporter and the No. 6 wheat exporter before Russia's invasion, according to International Grains Council data.

Senegal's President Macky Sall said Putin claimed to be ready to enable the export of Ukrainian grain to ease the global food crisis hitting Africa especially hard.

"The corn market has become very oversold, but the concern about the possibility of grain moving out of Ukraine remains," said Tomm Pfitzenmaier, analyst for Summit Commodity Brokerage. "If that does not happen, then the corn market is set up for a price rebound."

Most-active wheat futures ended 18-1/4 cents lower at $10.40 a bushel at the Chicago Board of Trade. Corn settled down 3-1/4 cents at $7.27 a bushel, while soybeans dropped 31-1/2 cents to $16.97-3/4.

In other news, the U.S. Environmental Protection Agency issued biofuel blending mandates for 2022 and the prior two years - with this year's number below one proposed in December.

(Reporting by Tom Polansek in Chicago, Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Aditya Soni, David Clarke and Jonathan Oatis)