German Defence Minister Boris Pistorius has warned that an EU pledge to provide Ukraine with a million artillery shells by March 2024 will not be met.
In March, the EU made a “historic decision” to provide Kyiv with a million 155-mm shells within a year.
Ukrainian forces have often complained of shortages in their war with Russia.
President Volodymyr Zelensky said one of the reasons this year’s highly anticipated summer counter-offensive did not start earlier was the lack of weapons and materiel.
Ukrainian officials said during the spring that Russian forces were firing 25,000-30,000 shells of different types a day, up to four times the number that Ukraine’s military could fire.
Twenty-five of the EU’s 27 members, along with Norway, signed up to a fast-track deal to hand Ukraine more ammunition through the European Defence Agency as a show of support for Kyiv and a signal to the arms industry.
The shells were to come from existing stockpiles and joint purchases. Traditionally, EU countries have made individual defence decisions until now, rather than pooling their resources in a united approach.
Mr Pistorius said that he personally had never promised a million shells and some voices at the time had questioned whether it had been a realistic ambition: “These warning voices have now been proven right, unfortunately.”
Ukraine’s foreign minister, Dmytro Kuleba, said there was enough political will in the EU to help Ukraine but he said bureaucracy and other obstacles were getting in the way. He highlighted “the pitiful state of the defence industry, the capability to produce enough ammunition, depots, and the ability to make external contracts”.
The EU’s foreign policy chief, Josep Borrell, blamed a lack of production capacity, suggesting that Europe’s defence industry needed to change its priorities from exporting 40% of its products to other countries.
But Nato Secretary General Jens Stoltenberg said other Western allies including the UK and US were stepping up production and he was encouraged that Germany and other EU countries were improving too.
The Pentagon said in September that it was producing 28,000 shells a month and aimed to reach 57,000 next spring, with the aim of helping Ukraine maintain the pace of its counter-offensive and resupplying US stockpiles.
President Zelensky warned on Tuesday that Russia was intensifying its attacks on the front line, around the eastern cities of Donetsk, Kupyansk and Avdiivka.
More than 1,500 civilians remain in Avdiivka, a strategically important town that overlooks Russian-held Donetsk 20km (12 miles) away.
The head of Avdiivka’s military administration, Vitaliy Barabash, said not a single building in the town remained intact: “Avdiivka and its strategic position is geographically located on heights and you can see Donetsk… from here. That’s why they need it.”
Separately, the governor of Ukraine’s southern Kherson region said three people were killed and 15 others wounded in Russian shelling on Tuesday.