US domestic politics are the reason why President Donald Trump cancelled a planned meeting with Russian President Vladimir Putin at this weekend's G20 summit, the Russian Foreign Ministry suggested on Friday.

"Was a provocation by Ukraine in the Kerch Strait really the reason for the cancellation? Publicly we have heard such an explanation," spokeswoman Maria Zakharova told reporters in Moscow.

"It seems to me that it's necessary to look for the answers in the US domestic political situation, which dominates decision-making," Zakharova said in comments carried by state news agency TASS.

Trump announced the cancellation on Twitter while on his way to the summit in Buenos Aires, citing a clash last weekend between the Russian coastguard and the Ukrainian navy in which the Russian side opened fire and seized Ukrainian vessels.

"Based on the fact that the ships and sailors have not been returned to Ukraine from Russia, I have decided it would be best for all parties concerned to cancel my previously scheduled meeting," Trump said, suggesting he could meet Putin "as soon as this situation is resolved."

The cancellation came hours after Trump's former lawyer Michael Cohen admitted lying to the US Congress about a Trump Tower real estate project in Russia in the period leading up to the last presidential election.

The Kremlin responded to the cancellation by saying Putin would now have more time for "useful meetings," according to comments carried by state media.