"We have given weapons to Ukraine, but in so doing, we realised that our military stockpiles have been depleted," he said in a statement.
Borrell also pointed out that the Ukraine conflict had been "a wake-up call" for the European Union about its military capabilities.
This is at least the second time Borrell has warned about Europe depleting its military stockpiles.
In September, Borrell stated that "The military stocks of most [European NATO] member states have been, I wouldn’t say exhausted, but depleted in a high proportion, because we have been providing a lot of capacity to the Ukrainians."
At that month's UN General Assembly meeting, NATO Secretary-General Jens Stoltenberg said that NATO members need to reinvest in their arms industry.