The US claimed on Friday that North Korea has provided arms for Moscow to use in Ukraine, releasing images the White House says shows containers moving into Russia by ship.
White House National Security Council spokesman John Kirby on a press call said that Pyongyang had provided Moscow with “more than 1,000 containers of military equipment and munitions”.
“We condemn [North Korea] for providing Russia with this military equipment, which was used to attack Ukrainian cities, kill Ukrainian civilians and further Russia's illegitimate war,” Mr Kirby said.
North Korea has built up a vast arsenal of artillery but is subject to a 2006 UN arms embargo that bans Pyongyang from exporting or importing weapons.
Washington is also “increasingly concerned” about Russian assistance to North Korea, Mr Kirby said.
He added that US intelligence has assessed Pyongyang is actively seeking military assistance from Russia, including in the form of fighter aircraft surface to air missiles, armoured vehicles, ballistic missile production equipment and “other advanced technologies”.
“We are monitoring closely whether Moscow will provide Pyongyang with these materials and we have already observed that Russian ships offloading containers in the DPRK which may constitute the initial deliveries of material from Russia,” Mr Kirby added, using North Korea's official abbreviation.
Last month, South Korean President Yoon Suk-yeol warned of the growing alliance between Russia and North Korea after a high-profile visit to Russia by North Korean leader Kim Jong-un, who met Russian President Vladimir Putin to discuss increasing military co-operation.
Meanwhile, the escalation of violence between Israel and Gaza has further complicated US President Joe Biden's promised support of Ukraine, which is already facing resistance from some Republicans in Congress.
Since Russia launched its invasion of Ukraine in February last year, the US has approved about $113 billion in military and humanitarian aid.
Defence Secretary Lloyd Austin on Thursday sought to assure allies at a Nato defence partners meeting that Washington “can and will stand by Israel, even as we stand by Ukraine”.
But members of Congress have expressed scepticism that there will be enough support to pair aid to Ukraine with aid to Israel.
A majority of Republicans in the House of Representatives opposed $300 million for the Pentagon to arm Ukraine two weeks ago.
“This is going to be a leadership call,” House Foreign Affairs Chair Michael McCaul told reporters this week after a classified briefing on the situation in Israel.
“They’ve had discussions with [the White House Office of Management and Budget].”
He added: We’re looking at a variety of options that would include all four of those things,” referring to funding for Ukraine, Israel, Taiwan and border security.