The Russian military could attack civilian shipping in the Black Sea as part of its effort to target Ukrainian grain facilities, Biden administration officials said Wednesday, citing new intelligence.

“Our information indicates that Russia laid additional sea mines in the approaches to Ukrainian ports,” National Security Council spokesman Adam Hodge said in a statement. “We believe that this is a coordinated effort to justify any attacks against civilian ships in the Black Sea and lay blame on Ukraine.”

The warning came just days after Russia ended the Black Sea grain deal that kept cargoes flowing through the corridor. The accord marked a rare example of Russian cooperation during its war against Ukraine.

Russia’s defense ministry said that all ships headed to the ports from Thursday would be considered as potentially carrying military cargo. It also said flag countries of vessels sailing to Ukraine would be considered as taking Kyiv’s side in the war.

Earlier: Wheat Surges Most in a Decade on Threat to Ukraine Exports

Wheat futures soared as much as 9%, the biggest jump since 2012, after Russia issued the threat, escalating a conflict over exports from the key Black Sea region.

“In addition to this coordinated effort in the Black Sea, we have already observed that Russia targeted Ukraine’s grain export ports in Odesa with missiles and drones on July 18 and 19, resulting in the destruction of agricultural infrastructure and 60,000 tons of grain,” Hodge added.