As G7 foreign ministers meet in Capri, the United States is hoping to persuade the Europeans to increase pressure on China, which Washington accuses of helping Russia's military expansion.

US Secretary of State Antony Blinken, who arrived on the Italian resort island on Wednesday, was to raise his concerns during a working session Thursday devoted to Russia's February 2022 invasion of Ukraine.

The Americans hope in particular that European nations will pressure China to reduce military support for Russia, at a time when, according to Washington, Russian forces are gaining ground in Ukraine.

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

"What we have seen over the past months, is that there have been materials moving from China to Russia that Russia has used to rebuild their industrial base, and produce arms that are showing up on the battlefield in Ukraine, and we are incredibly concerned about that," US State Department spokesman Matthew Miller said this week.

On Thursday, after meeting with Ukrainian Foreign Minister Dmytro Kuleba, Blinken stressed the "urgent" need to step up support for Ukraine, after another Russian strike on Wednesday left 18 people dead.

The US House of Representatives is expected to vote Saturday on new military aid including some $61 billion in long-delayed support for Ukraine.

"This is a matter of death and life," Kuleba said, adding that he would be working at the G7 meeting to secure more air defence support, which he said was of "fundamental importance".

- Blinken and China -

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.

The US pressure comes as Blinken prepares to visit China, a trip Washington says will come in the "coming weeks".

In Beijing on Tuesday, German Chancellor Olaf Scholz said he had asked Chinese President Xi Jinping to pressure Moscow to stop its "senseless" war in Ukraine.

The question of military support for Russia was also discussed in a recent conversation between President Joe Biden and Xi.

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

Unveiling US findings, officials said China was helping Russia on 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 revitalising Russia's defence industrial base "which had otherwise suffered significant setbacks" since Russia's invasion of Ukraine, a senior US official told reporters on condition of anonymity.

Washington said that China provided more than 70 percent of the $900 million in machine tools -- likely used to build ballistic missiles -- imported in the last quarter of 2023 by Russia.

US officials also said that 90 percent of Russia's microelectronics imports last year -- used to produce missiles, tanks and aircraft -- came from China.