G7 foreign ministers Friday expressed "strong concern" about transfers of dual-use materials and weapons components from Chinese businesses to Russia for use in Moscow's military expansion.

At a meeting in Italy, US Secretary of State Antony Blinken had urged European counterparts to increase pressure on Beijing, who Washington accuses of helping Russia's "most ambitious defence expansion since the Soviet era".

"We express our strong concern about transfers to Russia from businesses in the People’s Republic of China of dual-use materials and weapons components that Russia is using to advance its military production," the Group of Seven ministers said in a final statement after talks on the island of Capri.

"This is enabling Russia to reconstitute and revitalize its defense industrial base, posing a threat both to Ukraine and to international peace and security.

"China should ensure that this support stops, as it will only prolong this conflict and increase the threat that Russia poses to its neighbors."

In addition to the United States, the G7 countries include Canada, the UK, France, Germany, Japan, and Italy, which holds the presidency this year.

Washington has set a red line for Beijing -- not to supply weapons to Russia for its war in Ukraine. And so far it has not presented proof that this has been crossed.

But the United States is increasingly denouncing what it says is China's backdoor support for Moscow.

A senior US official said last week that China was helping Russia undertake "its most ambitious defense expansion since the Soviet era and on a faster timeline than we believed possible" early in the Ukraine conflict.

Unveiling US findings, officials said China was helping Russia in a range of areas including the joint production of drones, space-based capabilities, and exports vital for producing ballistic missiles.

China has been the key factor in revitalizing Russia's defense industrial base "which had otherwise suffered significant setbacks" since Russia's invasion of Ukraine, a senior US official told reporters on condition of anonymity.