President Donald Trump says Russia is helping North Korea get supplies in violation of international sanctions as Pyongyang gets ever "closer every day" to being able to deliver a long-range missile to the United States.
"Russia is not helping us at all with North Korea," Trump said during an Oval Office interview with Reuters on Wednesday. "What China is helping us with, Russia is denting."
Trump cast doubt on whether talks with Kim Jong Un would be useful.
He declined to say whether he had communicated with Kim, with whom he has exchanged insults and threats.
"I'd sit down, but I'm not sure that sitting down will solve the problem," he said, noting failed past negotiations.
Trump praised China for restricting oil and coal supplies to North Korea but said Beijing could do much more to constrain Pyongyang.
Western European security sources told Reuters in late December Russian tankers supplied fuel to North Korea on at least three occasions in violation of international sanctions. Russia has denied it.
North Korea relies on imported fuel to keep its struggling economy functioning and needs oil for its missile and nuclear program.
Trump has repeatedly blamed a US investigation into whether Russia meddled in the 2016 presidential election for hindering an improvement in relations.
"He can do a lot," Trump said of President Vladimir Putin. "But unfortunately we don't have much of a relationship with Russia, and in some cases it's probable that what China takes back, Russia gives. So the net result is not as good as it could be."
Trump said Pyongyang is steadily advancing in being able to deliver a missile to the United States.
"They're not there yet, but they're close. And they get closer every day," said Trump.
North Korea said after its last intercontinental ballistic missile launch in November that the test had put the US mainland within range. Some experts agreed it could fly as far as Washington DC.
North Korea hasn't shown it has mastered all technical hurdles, including development of a re-entry vehicle needed to deliver a heavy nuclear warhead reliably atop an ICBM.
Trump welcomed talks between North and South Korea over the Winter Olympics.
He would not say whether the US is considering a limited, pre-emptive attack.
"We're playing a very, very hard game of poker and you don't want to reveal your hand," he said.
