The UK and NATO forces have said Western military powers are running out of ammunition to give Ukraine to defend itself against Russia's full-scale invasion, which started in 2022.
Admiral Rob Bauer, NATO's most senior military official, told the Warsaw Security Forum as quoted as saying BBC that "the bottom of the barrel is now visible".
He said governments and defence manufacturers now had to "ramp up production in a much higher tempo".
Interestingly, Ukraine fires thousands of shells every day and most of them are supplied by NATO.
The admiral, who chairs NATO's Military Committee, told BBC that decades of underinvestment meant NATO countries had begun supplying Ukraine with weapons with their ammunition warehouse already half-full or even emptier.
"We need large volumes. The just-in-time, just-enough economy we built together in 30 years in our liberal economies is fine for a lot of things - but not the armed forces when there is a war ongoing," he said.
UK Defence Minister James Heappey told the forum, as quoted by BBC, that Western military stockpiles were "looking a bit thin" and urged NATO allies to spend 2% of their national wealth on defence, as they had committed to do.
"If it's not the time - when there is a war in Europe - to spend 2% on defence, then when is?" he asked.
"We can't stop just because our stockpiles are looking a bit thin," Heappey said, adding, "We have to keep Ukraine in the fight tonight and tomorrow and the day after and the day after. And if we stop, that doesn't mean that Putin automatically stops."
Travelling to Kyiv last month with the UK Chief of the Defence Staff, Defence Secretary Grant Shapps held meetings with the Ukrainian Defence Minister, Rustem Umerov, and made a personal commitment to continue the UK’s resolute support to Ukraine as they reclaim land taken following Putin’s illegal invasion.
The visit provided an opportunity to hold further discussions on military support with Umerov, after they first met in Ramstein, Germany, during a meeting of 50 nations at last week’s Ukraine Defence Contact Group.
Grant Shapps said: "It was an honour to meet President Zelenskyy in Kyiv to assure him that the UK will continue to stand shoulder to shoulder with Ukraine, as we have since Putin illegally invaded Crimea nearly ten years ago."
"We have trained tens of thousands of Ukrainian soldiers, delivered hundreds of thousands of rounds of ammunition, and provided millions of pounds of economic and humanitarian aid to help Ukraine’s citizens reclaim and rebuild what has been taken from them by Putin’s barbaric invasion," Shapps said.
"Having heard the experiences of so many Ukrainians affected by this war, including a family I hosted in my home for a year, I am committed to maintaining the UK’s military support – particularly as the freezing winter weather approaches," he said.
The UK said it has led the way in global support for Ukraine, having been the first country to provide modern, Western main battle tanks and long-range precision strike cruise missiles, following decisions by Prime Minister Rishi Sunak.
Further support has included more than 300,000 rounds of artillery ammunition, hundreds of vehicles and weapon systems, and thousands of items of personal protective equipment.
A UK-led international programme of training for Ukraine’s military, which is supported by ten other nations, has already trained more than 26,500 recruits and is on track to have trained more than 30,000 soldiers by the end of 2023.