"Right now, Ukraine for 155-millimeter shells is mainly dependent on US production. European production has just not been up and running yet," Cavoli said at a Senate armed services committee hearing.
Europe is, however, seeking to increase its 155-millimeter shell production and planning investments to accelerate the output, Cavoli said.
The top US general in Europe pointed to countries such as Slovakia as an example of production ramp-up but noted that much remains to be done.
"The EU and NATO are cooperating closely on lifting production, and I believe they're going to break down some barriers and get that going," Cavoli continued, adding that it would take several months before they reach US levels of output.
Russia has consistently warned the West against continued arms deliveries to Ukraine, arguing they will do nothing but escalate hostilities and prolong the conflict. Russian Foreign Minister Sergey Lavrov has warned that any military cargo will be a legitimate target for Russia.