The US is a major world power, so its internal affairs inevitably affect global issues, Russian President Vladimir Putin has said, commenting on the recent election debate between Joe Biden and Donald Trump.

The Russian leader admitted he had seen "fragments" of last week's debate between the Democratic and Republican rivals, but noted that he has more important things to do than follow all the twists and turns of the US electoral process, when asked about it at a press conference following the Shanghai Cooperation Organization (SCO) summit in Astana, Kazakhstan on Thursday.

"I have enough to do, so I don't really follow what's going on there, especially through the comments in the media. They always have certain preferences: someone is for, someone is against," Putin said.

Earlier this year, Putin claimed it would be better for Russia if Biden were reelected, describing the incumbent as "a more experienced and predictable person… a politician of the old sort" and waving off claims of the US leader's cognitive decline.

Asked whether the debate, described as "disastrous" for Biden even by allies, has somehow affected his opinion, Putin insisted that "nothing has changed," adding "didn't we all know what might happen?"

"But this is, in fact, their internal business," Putin stated, reiterating Moscow's readiness to work with whoever the Americans elect – but noting that the world cannot be completely "indifferent" to US politics.