U.S. grain and soybean futures rallied Friday, ending higher on growing optimism about export demand across the markets.

Soybean futures for March delivery at the Chicago Board of Trade climbed 9 1/4 cents to $12.67 1/2 per bushel, ending up 3.1% on the week. CBOT March corn futures, meanwhile, closed up 5 1/2 cents at $6.41 3/4 a bushel.

The markets were lifted by a series of exports announcements from the past week that continued Friday. The U.S. Agriculture Department announced fresh sales for soybeans, corn and wheat.

The largest of these sales by far was for soybeans to China, as part of a deal that was already known after a signing ceremony this week during a Chinese delegation's visit to Iowa. The sales totaled 2.923 million metric tons, almost all of which were for the 2012-13 marketing year, which starts in September. Skeptics pointed out that China could potentially cancel the deals later.

Still, the sales added to optimism that the U.S. would continue to see increased business as South America production falters in hot, dry weather, sending buyers elsewhere to find supplies. Drought conditions in Brazil in particular have boosted soybean futures this week.

"The market continues to put a large premium estimating South American production to be lower than current USDA estimates," E-Hedger said in a Friday report.

Traders said short-covering after recent losses, particularly in corn and wheat, which fell to three-week lows this week, added to the support Friday.

Corn and wheat are being pulled higher by soybeans, and also had their own support Friday from news out of Ukraine that fueled talk of much-lower-than-expected wheat exports out of the country.

APK-Inform, a Ukrainian agricultural analysis body, said many domestic exporters have stopped buying wheat from inland grain elevators, due to a government request to refrain from export activity until the fallout from severe frosts on winter crops is better known.

It added some traders felt compelled to comply with the request for fear of an official export regulation being imposed if the voluntary measure was flouted.

The restrictions would be supportive to corn even though Ukraine is a more important wheat exporter. Much of the nation's exports typically end up being used as livestock feed, displacing corn.

The USDA also announced fresh export sales of corn to South Korea and wheat to Egypt on Friday.

Wheat prices will remain tied to corn, traders said. CBOT March wheat ended up 15 1/4 cents to $6.44 per bushel, while Kansas City Board of Trade March wheat climbed 6 1/2 cents to $6.89 1/2. MGEX March wheat ended up 4 1/2 cents to $8.22 1/4, although deferred contracts were lower in a correction from Thursday's sharp jump.

Traders are looking ahead to the USDA's annual outlook forum to be held later next week. The government's estimates, and officials' comments, will be viewed as an early indication of U.S. supply and demand in the year ahead.