President Donald Trump has said that Russia was hurting United States efforts to disarm North Korea of its nuclear weapons, while China has been helpful.

In an interview with Fox Business Network, Trump said it would be easier to resolve the North Korea nuclear issue if the US had a better relationship with Russia.

"China is helping us and maybe Russia's going the other way and hurting what we're getting," Trump said of the North Korea situation.

Although North Korea signed the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in 1985, it has since then been found by the International Atomic Energy Agency in noncompliance.

Pyongyang asserts it will keep building up its nuclear arsenal in "quality and quantity". US officials estimate it has 60 nuclear weapons, whereas independent experts estimate it has enough uranium to produce six new nuclear bombs a year.

In total, the US is in possession of 6,800 nuclear warheads. A partial test ban treaty was ratified by the US in 1963, but the Senate has since rejected ratification of the comprehensive test ban treaty.

"At the beginning of 2017, the US Defense Department maintained a stockpile of an estimated 4,480 nuclear warheads for delivery by more than 800 ballistic missiles and aircraft," reported the Bulletin of the Atomic Scientists.

In recent days, a series of weapons tests by North Korea and a string of increasingly combative exchanges between Trump and North Korean leader Kim Jong Un have ratcheted up tensions.

Trump has negotiated with China to help rein in North Korea's nuclear program. China, North Korea's sole major ally, accounts for more than 90 percent of trade with the isolated country.

Trump said in a tweet that he spoke with Chinese President Xi Jinping on Thursday and raised the issue of North Korea.

US-Russia relations have been strained over allegations that Russia had meddled in the 2016 US presidential election, Moscow's annexation of Crimea from Ukraine and its backing of the Syrian government.

"I think we could have a good relationship" with Russia, Trump said. "I think the North Korean situation would be easier settled."

Trump said during last year's campaign that he hoped to improve relations with Moscow.