By Ilan Brat

CHICAGO--U.S. wheat futures climbed on Friday, bolstered by new export sales and a weakening of the dollar.

Corn oscillated between gains and losses and soybeans were lower.

Wheat futures rose, in part because the greenback was down. A decline in the dollar helps make U.S. supplies more affordable for foreign buyers. The overall strength of the dollar in the last year has battered grains and soybeans in general and dragged particularly on wheat, one of the most global of grains. It has helped make European and Russian wheat more attractive to big buyers such as Egypt and relegated U.S. supplies to a position farther down buyers' preferences list.

But as wheat prices have declined to around $5 a bushel, some investors say it may be starting to stoke foreign demand.

On Friday morning, U.S. Department of Agriculture reported new export sales of wheat to unspecified destinations.

With wheat, "we're starting to get a little more into a value zone" that could drive foreign demand, said Jason Britt, president of Central States Commodities, a Kansas City, Mo.-based brokerage.

Chicago Board of Trade wheat futures for September delivery were recently up 4 1/2 cents, or 0.9%, to $5 3/4 a bushel.

Corn futures swung from gains to losses and gains again throughout the morning session. Mr. Britt said uncertainty about whether an extremely rainy June and early July and a subsequent spell of benign weather would make output more or less than expected was a big factor driving the volatility.

"It feels like we're caught up a little bit in the summer doldrums," he said.

CBOT corn futures for September delivery were recently down 3/4 cent, or 0.2%, to $3.72 1/2 a bushel.

Soybean futures came under pressure from a cancellation of an export order to China.

CBOT August soybean futures shed 8 1/4 cents, or 0.8, at $9.82 a bushel.

Write to Ilan Brat at ilan.brat@wsj.com

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