GRAINS-Wheat jumps 2 percent as Ukraine tensions rise

* Ukraine a major exporter of wheat

* Cold weather adds support to wheat prices -analysts

* Corn firms on Ukraine fears, soybean prices rebound

(Writes through with updated prices, details; changes byline, dateline) PARIS/SYDNEY, April 14 (Reuters) - U.S. wheat futures rose as much as 2 percent on Monday as tensions escalated in Ukraine, stoking fears of potential disruptions in supply from one of the world's largest exporters. Corn climbed 0.9 percent, in its first daily gain in four sessions, on the rising uncertainty in Ukraine, while soybeans also firmed, rebounding slightly from losses of 2 percent in the previous two sessions when Chinese defaults weighed on prices. Chicago Board of Trade May wheat futures were up 1.7 percent at $6.71-1/2 a bushel at 1145 GMT, having earlier hit a session high of $6.89-1/2 a bushel, its highest level since the start of the month. Wheat closed down 0.3 percent on Friday. "If tensions between Ukraine and Russia intensify further, this could have a negative impact on wheat shipments from the Black Sea region, which would then increase demand from other exporting countries," Commerzbank said in a note. It added, however, that most of the exports out of the region, one of the world's largest wheat exporters, have already been processed. It also noted that European wheat futures had risen more modestly than in Chicago even if EU wheat would benefit more than U.S. wheat in the case of supply interruptions. Paris-based May was 1.1 percent higher at 202.75 euros a tonne. Tensions in the Black Sea region rose after Ukraine gave pro-Russian separatists a Monday morning deadline to disarm or face a "full-scale anti-terrorist operation" by its armed forces, raising the risk of a military confrontation with Moscow. Ukraine is forecast to export 9.5 million tonnes of wheat in the 2013/14 season, the U.S. Department of Agriculture said last week, having previously pegged sales at 10 million one month earlier. U.S. wheat prices also drew support from forecasts for further cold weather across the U.S. Plains, adding to concerns over potential crop damage. Updated weather models expect a cold front to hit key growing regions this week, with the condition of the U.S. winter wheat crop already at a 12-year low.

May corn futures rose 0.9 percent to $5.03 a bushel, having closed down 0.6 percent on Friday. The USDA pegged Ukraine corn exports at 19 million tonnes last week, up from its previous estimate of 18.5 million tonnes. May soybeans futures rose 0.27 percent to $14.67 a bushel, having closed down 1.3 percent in the previous session. Soybeans have come under sustained pressure in recent sessions after Reuters reported that Chinese importers defaulted on at least 500,000 tonnes of U.S. and Brazilian soybean cargoes worth around $300 million as buyers struggled to get credit amid losses in processing beans.

Prices at 1142 GMT

Product Last Change Pct Move End 2013 Ytd Pct CBOT corn 503.00 4.50 +0.90 430.25 16.91 CBOT soy 1467.00 4.00 +0.27 1312.50 11.77 CBOT wheat 671.75 11.50 +1.74 612.00 9.76 Paris wheat 212.25 2.50 +1.19 202.50 4.81 Paris maize 188.50 1.50 +0.80 171.75 9.75 Paris rape 416.00 -1.00 -0.24 366.50 13.51 WTI crude oil 103.60 -0.14 -0.13 91.82 12.83 Euro/dlr 1.38 0.00 -0.41 0.00 0.00 * CBOT futures prices are in cents per bushel, Paris futures in

euros per tonne, WTI crude oil in dollars per barrel.

(Reporting by Sybille de La Hamaide and Colin Packham; Editing by Joseph Radford and Anthony Barker)