CHICAGO  - U.S. wheat futures retreated on Thursday as worries over favorable weather dissipated and demand concerns resurfaced after top importer Egypt passed on U.S. wheat in a purchasing tender for a second straight day.

Soybean futures sagged on weaker-than-expected export sales and worries of diminished livestock feed demand, while corn firmed after hitting its lowest in 3-1/2-years a day earlier due to falling ethanol demand.

Chicago Board of Trade (CBOT) most-active wheat fell 10-1/2 cents to close at $5.29-2/4 a bushel, for a fourth straight day of declines that brought the market to its lowest close since March 18.

Corn was up a 1/2 cent at $3.19-3/4 a bushel after falling to its lowest since September 2016 on Wednesday, while soybeans shed 5-1/4 cents to $8.36-3/4 a bushel.

Wheat fell as early week weather concerns for Black Sea region and U.S. Plains crops faded and traders turned their focus to uncertain U.S. export prospects.

"Wheat joined up with the demand concerns of corn and beans, as opposed to worrying about the supply concerns of cold weather and the crop conditions," said Mike Zuzolo, president of Global Commodity Analytics.

U.S. wheat was offered at the lowest price in an international purchase tender from Egypt on Thursday, but the major importer chose grain from rival suppliers for a second straight day due to prohibitively high U.S. shipping costs.

Hopes had risen for revived U.S. exports after Romania announced an export ban last week to conserve domestic supplies during the coronavirus crisis. That followed export quotas announced by Russia and Ukraine to secure food supplies.

Soybeans continued to lag on poor export sales and uncertain livestock markets, which use the bean for feed.

"There's a divergence between meal and soy, and a lot of that falls at the feet of the record crush number we saw this week," said Zuzolo.

Export sales of soybeans were 304,700 tonnes last week, the U.S. Department of Agriculture said. That was below analysts' estimates ranging from 375,000 to 900,000 tonnes.

Corn export demand has been solid, but demand for corn-based ethanol has suffered as U.S. lockdown orders to prevent the spread of the new coronavirus have kept cars off the roads.

Weekly corn export sales totaled 969,500 tonnes, in line with trade estimates ranging from 750,000 to 1.550 million tonnes.

(Reporting by Christopher Walljasper in Chicago; Additional reporting by Michael Hogan in Hamburg and Naveen Thukral in Singapore; Editing by Jan Harvey, Dan Grebler and Peter Cooney) ((; +1 630 269 3072; Reuters Messaging: