SINGAPORE, July 21 (Reuters) - Chicago corn and soybeans slid on Tuesday as better-than-expected U.S. crop ratings weighed on prices, which climbed to multi-month highs in the previous session on strong demand and renewed fighting in the Middle East.

Wheat prices rose on worries about Black Sea shipments as escalating attacks on grain cargoes provided support.

FUNDAMENTALS

* The most-active corn contract on the Chicago Board of Trade (CBOT) fell 0.6% to $4.70-1/4 a bushel, as of 0020 GMT, having climbed to its highest since May 20 on Monday, while soybeans Sv1 gave up 0.3% to $12.23 a bushel, having reached their highest since May 13 in the last session.

* Wheat Wv1 rose 0.2% to $6.75-1/2 a bushel.

* The U.S. Department of Agriculture on Monday kept condition ratings for the nation's corn and soybean crops mostly steady from the previous week, surpassing analyst expectations from a Reuters poll of 11 analysts.

* The agency pegged condition ratings for the U.S. corn crop at 67%, one percentage point below the previous week's rating. Analysts had expected the agency would peg corn ratings at 66%.

* It said 66% of the U.S. soybean crop is in good-excellent condition, up a percentage point from the previous week and above analyst expectations.

* Wheat prices rose to a two-year high last week after attacks on grain ships and ports in the Black Sea and the Sea of Azov by Ukraine and Russia.

* Russian wheat export prices surged amid difficult shipping conditions in the Black Sea and a new wave of attacks in the Strait of Hormuz, analysts said on Monday.

* A Russian missile strike on a ship carrying corn near Ukraine's southern port of Odesa killed 10 people, Ukrainian officials said on Monday, in the deadliest attack in a weeks-long flare-up of violence in the Black Sea.

MARKET NEWS

* Major stock indexes fell on Monday with investors cautious about developments in the U.S.-Iran war and ahead of earnings from some high-profile U.S. companies this week. Oil prices gained. MKTS/GLOB

DATA/EVENTS (GMT)

0600 UK Claimant Count Unem Chng Jun

0600 UK ILO Unemployment Rate May

0600 UK HMRC Payrolls Change Jun

0900 Germany ZEW Economic Sentiment Jul

0900 Germany ZEW Current Conditions Jul