US vows 'firm' response to North Korea deployment in Ukraine conflict

US top diplomat Antony Blinken warned on Wednesday that the deployment of North Korean troops alongside Russian forces fighting on the Ukrainian border demanded a "firm response".

The secretary of state was speaking at the start of a day of Brussels talks with Nato and EU officials to urgently address ramping up support for Kyiv before Donald Trump reclaims the White House — potentially jeopardising future aid.

Addressing reporters alongside Nato chief Mark Rutte, Blinken said they had discussed the fact North Korean forces have been "injected into the battle, and now, quite literally, in combat which demands and will get a firm response".

The US State Department confirmed that thousands of North Korean troops — whose entry into the conflict marks a potentially major escalation — have begun "engaging in combat operations" alongside Russian forces in the Kursk region, near the border with Ukraine.

Blinken called it "a profound and incredibly dangerous development", without specifying what form a US response might take.

Rutte, meanwhile, stressed the crucial role played by China in helping Russia's "war effort", as well as by Iranian weapons deliveries — paid for with Russian funds that were in turn helping Tehran to "destabilise the Middle East".

Blinken took part in a meeting of the North Atlantic Council, Nato's decision-making body, before talks with Ukraine's Foreign Minister Andriy Sybiga, with the European Union's top diplomat Josep Borrell and his successor Kaja Kallas.

His emergency trip comes as Trump's election victory, coupled with a political crisis in Germany, heightens fears about the future of assistance for Ukraine at a key point in the fight against Russia's invasion.

Blinken told reporters President Joe Biden was "committed to making sure that every dollar we have at our disposal will be pushed out the door between now and January 20", when Trump takes office.

But he also reiterated the call for Washington's allies to step up.

"We're counting on European partners and others to strongly support Ukraine's mobiliaation," Blinken said, calling for more artillery, more air defences, more munitions as well as training for Kyiv's forces.

Trump has in the past voiced admiration for Russian President Vladimir Putin and scoffed at the $175 billion the United States has committed for Ukraine since the start of the war in 2022.