Ukraine has received only 10% of the US military aid approved by Congress earlier this year, President Volodymyr Zelensky said in a video quoted by "Reuters".
Ukraine is bracing for what could be its worst winter since the war began after Russian long-range airstrikes destroyed what officials say is about half of its energy-generating capacity.
"You're doing your job. You rely on reserves, you rely on special brigades, you rely on such equipment. And if you get 10% of all that (which) has already been voted... it's not funny," Zelensky said in English to Scandinavian journalists on Tuesday.
A $61 billion aid package from the United States, stalled by congressional Republicans since last December, was approved in April.
Zelensky added that the slow pace of arms deliveries is not a matter of funding.
"It's always about bureaucracy or logistics, ideas or skepticism... We'll give you this, we won't,'' he said.
He also said NATO countries had promised to supply Ukraine with six or seven air defense systems, which Ukraine increasingly relies on to repel long-range Russian strikes, by early September, but Kiev still didn't get them all.