US Secretary of State Antony Blinken demanded Russia allow grain shipments out of war-battered Ukraine during closed-door G20 talks in Indonesia on Friday, a Western official said.

"To our Russian colleagues: Ukraine is not your country. Its grain is not your grain. Why are you blocking the ports? You should let the grain out," said Blinken, according to a Western official present.

Blinken has refused to meet Russian Foreign Minister Sergei Lavrov but addressed Russia during the talks and laid out US financial assistance to ease global food shortages triggered by the war in Ukraine, a major source of global grain and corn exports.

"Russia is the source of the problem, the United States is focused on solutions," Blinken said, according to the official.

Ukraine has seen its production blocked by Moscow's military offensive, sparking a surge in prices that has particularly affected poor countries.

Moscow says it would allow Ukrainian ships loaded with food products to leave if the Ukrainian military demined its ports, an option rejected by Kyiv, which fears for the safety of its Black Sea coast.