CHICAGO, Jan 26 (Reuters) - U.S. wheat, corn and soybeans jumped on Thursday on support from a government report that showed strong overseas demand for all three commodities, traders said.

"We had some decent export sales compared to what we have seen the last few weeks and that trend, particularly for corn and wheat, is likely to continue," said Jim Gerlach, president of broker A/C Trading.

Wheat futures posted the biggest gain, with the most-active Chicago Board of Trade soft red winter wheat futures contract rising 1.5% after the U.S. Agriculture Department report showed the biggest weekly wheat sales since August.

Traders said the gains in corn and soybeans were capped by the upcoming South American harvest.

The grains received additional support from concerns that the crops of key supplier Ukraine will be smaller due to the war, and that Russia's crop also will fall below expectations.

CBOT March soft red winter wheat settled up 11-1/4 cents at $7.52-1/2 a bushel, and CBOT March corn was up 7-3/4 cents at $6.82-1/2 a bushel.

Ukraine's corn and wheat production is set to fall for a second year in 2023, with corn output not expected to exceed 18 million tonnes and wheat production 16 million tonnes as farmers reduce planting. Mark Jekanowski, chairman of the USDA's World Agricultural Outlook Board, told Argus Media's Paris Grain Conference that the agency's analysis of weather and previous crops does not support such a high crop as Russia estimates.

CBOT March soybeans gained 21 cents to settle at $15.23-1/2 a bushel.

The U.S. Agriculture Department's weekly report on Thursday morning showed that export sales of soybeans totaled 1.275 million tonnes in the week ended Jan. 19, topping market expectations.

Corn export sales of 925,900 tonnes and wheat export sales of 561,400 tonnes were in line with trade estimates. (Reporting by Mark Weinraub in Chicago Additonal reporting by Naveen Thukral in Singapore and Sybille de La Hamaide in Paris Editing by Jan Harvey and Matthew Lewis)