US President Joe Biden has landed in Brussels in the middle of a dispute with European allies over whether to impose further energy sanctions on Russia over its invasion of Ukraine.

Russia supplies about 40 per cent of the natural gas Europe uses, making it difficult for several European nations to ban energy imports as the US has.

Russian President Vladimir Putin said on Wednesday Russia will seek payment in roubles for gas sales to “unfriendly” countries, a move that sent European gas prices soaring on concerns it would exacerbate the region’s energy crunch.

Moscow’s list of unfriendly countries corresponds to those that imposed sanctions and includes Australia, New Zealand, the US, European Union members, Britain and Japan, among others.

Reducing Europe’s reliance on Russian energy has been a “substantial” topic and the subject of “intense back and forth” in recent days, White House national security adviser Jake Sullivan said on the Air Force One flight to Brussels.

Mr Sullivan said Mr Biden would have some news to announce on the topic on Friday, alongside European Commission President Ursula von der Leyen.

On Thursday, Mr Biden will attend an emergency NATO summit, meet with G7 leaders and address the 27 leaders of the European Union at a session of the European Council.

Mr Biden will later visit Warsaw for consultations with Polish President Andrzej Duda.

Mr Sullivan said G7 leaders would also agree on Thursday to co-ordinate on sanctions enforcement.

A French presidency official noted the European Union collectively trades more with Russia than the US does and is therefore more sensitive to sanctions.

“Americans have sanctioned Russian gas and oil, which is easier for them since they are producers. We will see what President Biden proposes tomorrow,” the official told Reuters.

Mr Sullivan said Mr Biden would on Thursday announce a US package of Russia-related sanctions on political figures and oligarchs.

The leaders will also discuss China.

Mr Biden has warned Chinese President Xi Jinping not to provide material support to Russia in its war against Ukraine.

Mr Sullivan said the US had yet to see evidence of Beijing sending aid to Moscow.

“But it’s something we’re watching every day,” he said.

Western leaders have grown increasingly concerned that Mr Putin will use chemical weapons or otherwise escalate tactics four weeks into an invasion where his troops have failed to capture a single major Ukrainian city.

Leaving the White House on Wednesday, Mr Biden said Russia’s use of chemical weapons in Ukraine was a “real threat”.

Mr Sullivan said Mr Biden would co-ordinate on the next phase of military assistance to Ukraine and would discuss with allies in Brussels “how to deal with the rhetoric and commentary on potential use of nuclear weapons” by Russia.

In recent days, Russia and Western governments have traded accusations over the possibility of a chemical weapons attack in Ukraine without producing evidence to back their concerns.

Mr Biden has vowed not to engage in direct conflict with Russia but has pledged the US will defend all NATO territory. He has ordered more US troops to NATO’s eastern flank to reassure edgy allies.

– AAP