The United States and its allies are working "day in and day out" to prevent transfers of weapons to Russia from countries including China, Iran, and North Korea to bolster the Russian military in its invasion of Ukraine, Secretary of State Antony Blinken said Tuesday.

The West is concerned that the transfer of supplies such as cheap drones from Iran, artillery rounds from North Korea, and the potential of deliveries from China could tip the balance in the conflict over two years after Russia invaded Ukraine.

"We are working day in, day out, to effectively prevent the transfer of weapons and materials to Russia, to fuel that war machine, to fuel the defense industrial base, including from Iran, from North Korea and China," Blinken told reporters in Paris.

"This is not just a threat to Ukraine, it's a threat to European security overall," he added.

South Korea's defense minister said last month North Korea has shipped around 7,000 containers of arms to Russia to use in its war with Ukraine since the transfers began around last July.

Tehran is already supplying drones to Russia, and G7 countries warned Iran last month that they would impose "significant" new sanctions if Tehran transfers ballistic missiles to Russia for use in Ukraine.

China meanwhile has insisted that it has not sold any lethal weapons for use in the conflict.

"We are working together to try to interrupt and penalize any provision of this kind of support whether from Iran, North Korea, or elsewhere including China," said Blinken.