MADRID, May 25 (Reuters) - Britain's Defence Secretary Ben Wallace on Wednesday called on Russia to let Ukraine export its grain to help countries where grain scarcity could trigger hunger.

Russia must "do the right thing," Wallace told reporters in Madrid where he met his Spanish counterpart Margarita Robles, and open a grain corridor from Ukraine's Black Sea ports.

On Thursday, Russian Deputy Foreign Minister Andrei Rudenko said the country was ready to provide a humanitarian corridor for vessels carrying food to leave Ukraine, in return for the lifting of some sanctions, the Interfax news agency reported.

Wallace rejected the idea of lifting sanctions, and welcomed the suggestion of Black Sea nations, such as Turkey, escorting the Ukraine grain shipments after Moscow ruled out the involvement of Western forces.

"That grain is for everyone, Libya, Yemen, people around the world are relying on that grain to feed themselves," Wallace said. "I call on Russia to do the right thing in the spirit of humanity and let the grain of Ukraine out, stop stealing the grain for its own means. Let's not talk about sanctions, let's do the right thing."

Ukraine's Black Sea ports have been blocked since Russia sent thousands of troops into Ukraine on Feb. 24 and more than 20 million tonnes of grain are stuck in silos in the country. (Reporting by Aislinn Laing, editing by Inti Landauro and David Evans)