Russian President Vladimir Putin's mutual defense agreement with North Korea has the potential to create friction with China, which has long been the reclusive state's main ally, the top U.S. military officer said Sunday.

"We've got someone else who's kind of nudging in now, so that may drive a little bit more friction between (China) and Russia," Air Force General Charles Q. Brown, chairman of the Joint Chiefs of Staff, told reporters during an overseas trip.

"So, it'll be interesting to see how these three countries — how this plays out."

Analysts said the pact, signed Wednesday, could undercut Beijing's leverage over its two neighbors and any heightened instability could be negative for China's global economic and strategic ambitions.

On Thursday, Putin said Russia might supply weapons to North Korea in what he suggested would be a mirror response to the Western arming of Ukraine.

Brown acknowledged U.S. concern about the deal.

But he also tempered those remarks by noting apparent limitations to the accord and expressing doubt Moscow would give North Korea "everything" it wanted.

U.S. officials have said they believe North Korea is keen to acquire fighter aircraft, surface-to-air missiles, armored vehicles, ballistic missile production equipment or materials, and other advanced technologies from Russia.

"The feedback I have on the agreement — it was a broad agreement that's not overly binding, which gives you an indication (that) they want to work together but they don't want to get their hands tied," Brown said.

The treaty signed by Putin and Kim on Wednesday commits each side to provide immediate military assistance to the other in the event of armed aggression against either one of them.

Putin has said Moscow expected that its cooperation with North Korea would serve as a deterrent to the West, but that there was no need to use North Korean soldiers for the war in Ukraine.

The United States and Ukraine say North Korea has already provided Russia with significant quantities of artillery shells and ballistic missiles, which Moscow and Pyongyang deny.