Arms negotiations between Russia and North Korea are actively advancing, a US official has stated, warning leader Kim Jong-un that his country would pay a price for supplying Russia with weapons to use in Ukraine.

Providing weapons to Russia "is not going to reflect well on North Korea and they will pay a price for this in the international community," US national security adviser Jake Sullivan told reporters at the White House.

The Kremlin said earlier on Tuesday it had "nothing to say" about statements by US officials that Kim planned to travel to Russia this month to meet President Vladimir Putin and discuss weapons supplies.

Kim expects discussions about weapons to continue, Sullivan said, including at leader level and "perhaps even in person".

"We have continued to squeeze Russia's defence industrial base," Sullivan said, and Russia is now "looking to whatever source they can find" for goods like ammunition.

"We will continue to call on North Korea to abide by its public commitments not to supply weapons to Russia that will end up killing Ukrainians," Sullivan said.

On Monday, US National Security Council spokeswoman Adrienne Watson said Kim and Putin could be planning to meet, and the New York Times cited unnamed US and allied officials as saying Kim plans to travel to Russia as soon as next week to meet Putin.

Asked if he could confirm the talks, Kremlin spokesman Dmitry Peskov said: "No, I can't. There's nothing to say."

As Russia's isolation over its war in Ukraine has grown, it has seen increasing value in North Korea, according to political analysts.

For North Korea's part, relations with Russia have not always been as warm as they were at the height of the Soviet Union but now the country is reaping clear benefits from Russia's need for friends.

A North Korean defence ministry official in November said the country has "never had 'arms dealings' with Russia" and has "no plan to do so in the future".

Russia's Defence Minister Sergei Shoigu, who visited Pyongyang in July to attend weapons displays that included North Korea's banned ballistic missiles, said on Monday the two countries are discussing the possibility of joint military exercises.