* CBOT wheat up 40% this week as war chokes Black Sea exports

* CBOT corn hits highest since 2012

* Russia recommends fertilizer producers suspend exports

CHICAGO, March 4 (Reuters) - Chicago Board of Trade wheat futures were on track for the biggest weekly gain on record as prices on Friday jumped by their daily limit on deepening fears the Ukraine war will cause prolonged disruptions to exports from the Black Sea region.

Trading was highly volatile as traders sought to assess how much demand may shift to the United States and how the conflict will hamper crop plantings in Russia and Ukraine.

The most actively traded wheat futures climbed 6.6%, or 75 cents, to a 14-year high of $12.09 a bushel by 11 a.m. CST (1700 GMT). The contract is up 40.6% for the week.

With Ukrainian ports closed and operators reluctant to trade Russian wheat in the face of Western financial sanctions, buyers are trying to find alternatives.

Russia's trade and industry ministry on Friday recommended the country's fertilizer producers temporarily halt exports, in a sign that sanctions imposed after Russia's invasion of Ukraine could have a global impact.

"If anything, things look scarier than they did yesterday," said Jim Gerlach, president of broker A/C Trading in Indiana.

CBOT corn rose to its highest since September 2012 at $7.82-1/2 a bushel retreating as traders booked profits, brokers said. The most-active May contract was down 8-1/2 cents at $7.39-1/4. In 2012, the market reached a record $8.49.

CBOT soybeans were down 20-1/4 cents at $16.47-1/2 a bushel. Traders weighed the loss of sunflower oil exports from Ukraine and Russia against improved soybean crop conditions in South America and profit-taking in palm oil markets.

Russia and Ukraine account for about 29% of global wheat exports, 19% of corn exports and 80% of exports of sunflower oil, which competes with soyoil.

In Europe, nearby wheat futures positions on Euronext reached the 400-euro mark for the first time.

"The demand for wheat on the physical market in (nearby) delivery is unprecedented, as buyers face delivery defaults for Black Sea origins," consultancy Agritel said. (Reporting by Tom Polansek in Chicago, Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Marguerita Choy)