America's top diplomat is vowing a "firm response" to reports that North Korean troops have entered combat alongside Russian forces in Ukraine.
In recent days, both the US State Department and South Korea's spy agency claimed troops from the north had engaged in combat on the Ukrainian frontline.
Russia and North Korea both officially ratified a mutual defence treaty this week, which gave assurances that both countries would come to each other's aid in case of an armed attack.
Russia began a full-scale invasion of Ukraine in February 2022, and now holds vast parts of the country's eastern regions.
US Secretary of State Blinken told reporters on Wednesday, local time, that the deployment of North Korean troops represented "a profound and incredibly dangerous development".
He did not outline what steps the US would be willing to take, but reiterated a call for NATO members to continue backing Ukraine with artillery, air defences, munitions and training.
"We're counting on European partners and others to strongly support Ukraine's mobilisation," he said.
On Wednesday, Ukrainian Foreign Minister Andrii Sybiha said he was "cautiously optimistic" about the possibility of conducting deep strikes on Russia, after a discussion with Mr Blinken.
[MAP]Mr Blinken's emergency trip comes as Donald 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.
The senior diplomat said outgoing US 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.
Seoul confirms North Korean troops on the frontline
South Korea's spy agency, the National Intelligence Service (NIS), on Wednesday said North Korean troops were now engaged in frontline combat in Ukraine.
"The [NIS] estimates that North Korean troops dispatched to Russia have moved to the Kursk region over the past two weeks," the agency said in a statement.
There has been international concern over the decision for Pyongyang to send approximately 10,000 soldiers to the Russian region of Kursk.
This year, Ukraine's military launched a counteroffensive into the Kursk region, and has been fending off attempts by Russian to force them back.
The small parcel of Russian land held by Ukraine could prove to be a useful bargaining chip, if Trump makes good on a promise to conduct peace talks between the two sides to end the war.
The former president has previously voiced criticism at the $US175 billion in military aid that the US has provided to Kyiv since the start of the war.
The 78-year-old tycoon has boasted he can end the war in a day, likely by forcing concessions from Ukraine, although his newly named national security advisor, Mike Waltz, said Trump may also pressure Russian President Vladimir Putin.
Russia launches early morning missiles, drones at Kyiv
The speculation on Ukraine's future came as Russia on Wednesday launched a wave of drones and missiles at the Ukrainian capital, killing at least one person and injuring another.
It was the first aerial assault on Kyiv in 70 days, authorities said.
Ukraine's air force said it had downed four missiles and 37 drones across the country overnight.
The attack is the latest in an uptick in escalating strikes on Ukrainian cities, mainly in the south of the war-battered country.
"It is important that our forces have the means to defend the country from Russian terror," President Volodymyr Zelenskyy said in response to the attack.
In recent months, Mr Zelenskyy has been urging Western allies for more air defence equipment to fend off attacks on cities and infrastructure.
The Kremlin has repeatedly denied its forces target civilians in Ukraine, a claim its spokesman repeated Wednesday in response to a question over whether Russian forces were working to minimise civilian casualties.
Reuters/AFP