Poland's Prime Minister, Mateusz Morawiecki, has said that direct intervention by U.S. Joe Biden is necessary to secure South Korean artillery shells desperately needed by Ukraine.

The Polish prime minister, who is visiting the United States, made the remarks in an interview with the New York Times on Wednesday.

Morawiecki reportedly told the newspaper that Russia’s military has far more artillery shells than the Ukrainian Army and tapping into South Korean stocks is crucial to providing much needed ammunition.

The Polish prime minister added that although Warsaw has spoken to Seoul about the delivery of weapons and munitions, any such deal is contingent on the intervention of the U.S. to overcome South Korea’s concerns about an aggressive response from China or Russia.

He expressed belief that such a deal would require direct assurances from President Biden that the U.S. would offer support to South Korea in the face of any backlash from the two neighboring countries.

Morawiecki added that his country, which has purchased many weapons systems from South Korea, would never transfer weaponry without negotiating an arrangement between the two sides.