Securing the shells has been a priority for Kyiv, which is burning through its reserves as Russia throws manpower and resources in a bid to make territorial gains.

Foreign Minister Dmytro Kuleba told top European diplomat Josep Borrell at a press conference in Kyiv that he expected the EU to ease regulation and sign "long-term contracts" with defence companies to boost shell production.

"If you ask a soldier at the front what he needs most now, the answer will be shells," Kuleba told Borrell.

"Because the scale of the war and Russia's use of artillery reached a level for which, let's be honest, the European defence industry was not ready," he added.

Kuleba also said Ukraine found infighting in the US Congress over the future of American aid "confusing", days after Republican lawmakers resisted new support for the war-torn country.

EU leaders overcame long-running opposition from Hungary to agree an aid package of 50 billion euros ($54 billion) for Ukraine last week, but support from Washington is still in doubt due to Republican resistance.

"Last night I received the latest report from Washington on possible scenarios, and some of the scenarios are reminiscent of a thriller story. Everything is very confusing," Kuleba said.