LONDON/MUMBAI - U.S. wheat futures hit a three-week low on Thursday, while U.S. corn also fell on lingering hopes that stuck grain supplies from the Black Sea region could start moving.

Soybeans, meanwhile, eased on concerns over demand from top consumer China.

The most-active wheat contract on the Chicago Board of Trade (CBOT) was down 2.57% at $11.18-1/3 a bushel at 1121 GMT, having hit its lowest since May 5 at $11.15. CBOT corn fell 1.7% to $7.59-1/4 a bushel, after hitting a seven-week low on Wednesday.

Russia is ready to set up a humanitarian corridor for vessels carrying food to leave Ukraine in return for the lifting of some sanctions, the Interfax news agency cited Russian Deputy Foreign Minister as saying on Tuesday.

Russia's U.N. Ambassador said on Wednesday Western officials need to talk to Ukraine about its grains exports. The officials countered that any deal on access to Ukrainian ports would need Russian agreement due to security concerns.

"I'd be very surprised if these corridors open. It would be a huge about-face for Russia and it won't come without some serious conditions," said a London-based grains dealer.

He added, however, that the grains market was so over-bought the slightest hint of supply relief was prompting selling.

Russia and Ukraine together account for nearly a third of global wheat supplies. Ukraine was the world's fourth-largest corn exporter in the 2020/21 season, according to International Grains Council data.

"The market is skeptical (about the corridors). Port infrastructure in Ukraine was badly damaged and it needs time to restore," said a Mumbai-based dealer with a global trading firm.

Soybeans dipped 0.1% to $16.80 a bushel.

They are under pressure because of plunging demand for soyoil in China, which has seen reduced consumption as lockdowns to prevent the spread of COVID-19 shutter restaurants and canteens.

Against that, soyoil shipments into India, the world's biggest importer of vegetable oils, could jump to a record after New Delhi allowed duty free imports.

Elsewhere, grain traders are also awaiting weekly U.S. export sales figures on Thursday for an update on overseas demand.

(Reporting by Maytaal Angel in London and Rajendra Jadhav in Mumbai; editing by Shailesh Kuber)