The top US diplomat says the circumstances surrounding the armed rebellion over the weekend by the Russian private military firm Wagner Group have exposed "some very serious cracks" in Russia.

US Secretary of State Antony Blinken spoke in an interview with ABC News on Sunday. He discussed Wagner's aborted advance toward Moscow, which had been ordered by its leader, Yevgeny Prigozhin.

Blinken said Wagner's move is not a surprise as tensions had already been rising for months due to Prigozhin's public criticism of Russian President Vladimir Putin's administration.

The secretary said Prigozhin also openly challenged Putin's leadership while publicly questioning the premise cited by Russia for its aggression against Ukraine.

Blinken said the invasion has made Russia "weaker" economically and militarily, with its global standing plummeting.

The secretary said that with the internal dissension in Russia, it is impossible to speculate on where the situation goes. But he stressed that the US is focused on Ukraine.

Blinken also spoke to CBS News on Sunday, saying the US has not seen any change in Russia's nuclear posture. But he added that Washington is going to watch developments in Russia "very, very carefully."