U.S. wheat rose on Wednesday, extending gains into a second straight session on expectations of increased export sales and hopes U.S. supplies could win part of a snap wheat purchase tender from Egypt.

Soybeans slipped on signs of falling demand, pulling corn down in their wake.

"We are seeing support for wheat today from hopes of more export sales by the U.S. with the attention on the large purchase tender from Egypt later today in which U.S. wheat has a good chance of winning," said Ole Hansen, head of commodity strategy at Saxo Bank.

"Soybeans are still suffering from the impact of signs that demand is fading as illustrated by China's cancelled purchases on Tuesday, while corn continues to be pushed down by the soybean weakness."

Chicago Board of Trade March wheat rose 0.8 percent to $8.17-3/4 a bushel by 1157 GMT after rising 0.56 percent on Tuesday. EU benchmark March wheat in Paris was up 0.4 percent at 255.25 euros a tonne.

Egypt's state buying agency GASC set a tender on Tuesday to buy an unspecified volume of wheat for Feb. 11-20 shipment. GASC is seeking cargoes of 55,000 to 60,000 tonnes of wheat, including two different classes of U.S. supplies, with results likely later on Wednesday.

"U.S. wheat has become more competitive into wider markets," said Rabobank analyst Graydon Chong. "It is starting to work into places like Egypt, and we expect the U.S. to get some action from their latest tender."

European traders also tipped the U.S. to get a slice of the Egyptian tender. "I think U.S. and French supplies will go head to head on the Egyptian tender today with no serious competition from other regions," one European trader said. "I do not expect there to be offers from Argentina following their recent harvest problems."

"Australia and Canada are also not expected to offer to Egypt, while Taiwan also issued a tender for U.S. wheat today, underlining the good global demand."

Chicago March soybeans fell 0.05 percent to $14.59-3/4 a bushel and Chicago March corn slid 0.1 percent to $7.19-1/4 a bushel after closing down 0.52 percent on Tuesday.

Soybeans were again weighed down by signs of falling demand.

China, the world's largest consumer of soybeans, cancelled 300,000 tonnes of U.S. supplies, while the U.S. Agriculture Department said the soybean cancellations also included 120,000 tonnes sold to unknown destinations. Despite indications of easing international demand, South American soybean production prospects continue to look mixed.

Widespread rainfall moved across Argentina over the weekend causing another slowdown in crop seedings and the rain is expected to continue through Wednesday, Global Weather Monitoring said.

Sluggish demand for U.S. corn was also burdening prices.

"Russian corn is still going onto export markets while a series of smaller buyers are still turning to South America as shown by the Oman tender today," a European trader said.

Market participants said the Christmas season factor is now fully visible.

"It must be stressed that we are at a time of year when market liquidity is drying out ahead of the Christmas and new year holidays and so fundamental news tends to have a larger than normal impact on prices," said Saxo Bank's Hansen.

"I think most financial investors have not yet made their decisions about their 2013 positioning. We are likely to see the impact early next week about the decisions made about where money should be placed in grains from early January."