Ukraine on Friday urged the West to "get serious" about curbing Russia's arms production by shutting loopholes that allow it to keep sourcing key parts.
Western countries have sanctioned swathes of Russia's weapons industry and banned the export of military goods and parts that it says helps Moscow's invasion of Ukraine.
But Kyiv says Russia is still getting hold of crucial components made by Western firms.
"The West must get serious about strangling Russia's ability to produce weapons," Ukrainian Foreign Minister Dmytro Kuleba said in a social media post.
"According to some data, up to 95% of the foreign-produced critical components found in Russian weapons destroyed in Ukraine come from Western countries," he added.
Kuleba said private firms are exporting civilian or so-called "dual use" goods that contain parts that can be used for arms.
He did not provide evidence for the claim, but Kyiv regularly disassembles Russian missiles and drones that fall on its territory to analyse their components.
Russia fires dozens of high-tech missiles and drones at Ukraine every week. Iran has supplied Moscow with drones, while Western intelligence says North Korea is sending artillery shells and rockets.
Moscow has also massively ramped up its domestic arms production, and Kyiv has recently stepped up its calls to ensure Western goods do not find their way to Russian weapons factories.
"Ukraine would require less assistance and would lose fewer lives if all of the murky schemes and sanction evasion loopholes were thoroughly tracked down and completely closed," Kuleba said.
Speaking in Davos at the World Economic Forum earlier this week, President Volodymyr Zelensky said the West needed to "ensure that sanctions work 100%."
Ukraine is also facing its own shortage of ammunition, officials in Kyiv have conceded.
There are concerns that the West's multi-billion-dollar military aid could be cut amid domestic political wrangling in both Europe and the United States.
