The European Union pledged last year to deliver the desperately needed ammunition to Ukraine by March 2024 to help Kyiv battle against Russia's invading forces.

So far, EU nations have only managed to provide 300,000 rounds from their existing stocks.

Countries are now placing joint orders for 155-millimetre shells but there are doubts over the capacity of defence companies to churn out enough in time.

"Unfortunately, the cautionary voices are now right," German Defence Minister Boris Pistorius said at a meeting with his EU counterparts in Brussels.

"The one million will not be reached. We have to assume that."

EU officials insist it is still too early to say the target won't be hit, despite growing scepticism it can be attained.

EU foreign policy chief Josep Borrell said a major issue was that European defence firms were exporting about 40 percent of production to other countries.

"Maybe what we have to do is to try to shift his production to the priority one, which is Ukrainian. That would be quite a change," he said.

EU internal market commissioner Thierry Breton said efforts to ramp up production were having an impact and the EU should be able to churn out a million shells a year.

- EU must deliver -

Estonian Defence Minister Hanno Pevkur said his country had placed a 280-million-euro order for ammunition -- "the biggest procurement in Europe at this very moment".

"We will try to do the maximum to deliver the shells to Ukraine because they need it," he said.

"Look at Russia. They are producing today more than ever. They are getting shells from North Korea. Europe cannot say that Russia and North Korea can deliver and we cannot."

The EU's struggles to make good on promised deliveries comes as opposition in the United States Congress has thrown doubt on key ally Washington's ability to sustain supplies.

On the ground, fighting appears to have ground to a stalemate as a much-anticipated Ukrainian counter-offensive has failed to win back much territory.

Brussels says that together with EU member states it has funnelled military support worth 27 billion euros ($29 billion) to Ukraine since Moscow invaded in February 2022.

Borrell in July proposed a new 20-billion-euro fund over the next four years to help cover arms deliveries to Ukraine.

The plan was part of a broader G7 vow to provide Kyiv long-term security commitments to help it ward off Russian aggression.

But discussions over the EU initiative have stalled amid doubts from key member states.

Germany -- which last week said it would double its own funding for Ukraine to eight billion euros next year -- is reluctant to commit more money to the EU pot.

Borrell said the EU would present a revised plan to Ukraine by the end of the month ahead of a debate by EU leaders in December on approving it.