PARIS - Chicago wheat fell more than 3% on Friday on expectations of higher supplies from the Black Sea region as Russia and Ukraine are due to sign a deal to open ports for grain shipments.

Corn and soybeans extended their fall in the previous session to hit a 8-month and 7-month lows respectively as forecasts of favourable U.S. weather eased global supply worries.

Russia, Ukraine and the United Nations are due to sign a deal on Friday at 1330 GMT to reopen Ukraine's Black Sea ports to grain exports, a hopeful sign that an international food crisis caused by Russia's invasion could be eased.

Turkish President Tayyip Erdogan said on Friday he would give good news to the world about grain exports after the signature. Ukraine and Russia are both among the world's biggest exporters of food.

"A serious deal would be a game-changer and potentially could bring millions of tonnes of Ukrainian grains into the market in coming weeks and months," one German trader said. "But the devil will be in the detail with so many serious problems to be solved."

The most-active wheat contract on the Chicago Board of Trade (CBOT) gave up 3.2% to $7.80-1/4 a bushel and soybeans lost 0.5% to $12.95 a bushel. Corn fell 1.1% to $5.67 a bushel, after dropping to its lowest since Nov. 30 at $5.63-1/2 a bushel. U.S. wheat exports have been gaining since the Russia-Ukraine war curbed shipments earlier this year.

U.S. wheat exporters last year notched up their second-worst performance in a half-century with global market share at an all-time low, as competing wheat offerings were plentiful and cheaper, Karen Braun, a market analyst for Reuters, wrote in a column.

Egypt's state grains buyer is believed to have bought an additional 120,000 tonnes of Russian and French wheat on Thursday, traders said, after booking 640,000 tonnes a day earlier. Buyers from China purchased large volumes of Australian and French wheat this week in a sign that the Asian country is taking advantage of a recent dip in prices to fill its large needs, European traders said on Friday.

Corn and soybean prices have been pressured by crop weather in the U.S. Midwest where corn is pollinating, its key reproductive phase, later than usual.

Forecasts called for beneficial rains and moderating Midwest temperatures next week. Commodity funds were net sellers of CBOT soybean, corn, wheat, soyoil and soymeal futures contracts on Thursday, traders said. 

(Additional reporting by Naveen Thukral and Michael Hogan; Editing by Sherry Jacob-Phillips and David Evans)