EU counterparts blamed France on Friday for delaying approval of a plan for the bloc to jointly buy desperately-needed ammunition for Ukraine.
Kyiv has urged its allies to ramp up supplies of howitzer shells as its forces struggle with shortages in the face of Russia's grinding assault and prepare to go on the offensive themselves.
The EU agreed in March to a two-billion-euro ($2.2 billion) proposal aimed at supplying a million shells to Ukraine over the next 12 months.
A first part of the one billion euro plan to get EU countries to raid their stockpiles urgently for ammunition was signed off last week.
But a second track to jointly purchase another billion euros of shells for Ukraine remains snarled over a dispute about whether they should be wholly manufactured within the EU.
In March, EU leaders agreed to source the ammunition from the "European defence industry" and Norwegian producers, as Oslo is also part of the scheme.
But European diplomats complained that France, a fierce protector of its own defence industry, is now insisting that this means manufacturing must be entirely done inside the EU.
That would exclude shells made in plants outside Europe, such as the one majority-owned by German giant Rheinmetall in Australia.
Diplomats from several EU states said there were doubts as to whether EU producers could make enough arms without recourse to outside suppliers.
"The goal of what we're trying to do is helping Ukraine -- everything else is secondary," a diplomat said.
Ukraine's Foreign Minister Dmytro Kuleba on Thursday lashed out at the EU's "frustrating" inability to reach a final deal.
"This is a test of whether the EU has strategic autonomy in making new crucial security decisions. For Ukraine, the cost of inaction is measured in human lives," he said, in a social media post.
After the complaint, EU foreign policy chief Josep Borrell spoke with Kuleba to reassure him that the EU would honour its promise, adding that two-thirds of the first billion-euro order had been delivered.
EU foreign ministers are expected to discuss the issue at a meeting in Luxembourg on Monday and diplomats said they hoped a final agreement could be reached next week.
A senior EU official insisted that the haggling was not holding up the supply of ammunition to Ukraine as shells were already being sent from stockpiles.
"We are working very hard so the ammunition will get to Ukraine," the official said, speaking on condition of anonymity. "It will be delivered on time."
