"Our attitude to NATO is well known: it's a product of the Cold War and the confrontation of the Cold War, Kremlin spokesman Dmitry Peskov told journalists.

"It's an alliance that was constructed with the aim of and in the name of confrontation," he said.

A NATO summit opens in Brussels on Wednesday, with the agenda including US President Donald Trump's demands for extra spending from allies along with the growing threat members see from Russia on its eastern flank.

"What the alliance is doing in the long run -- advancing towards our borders, expanding NATO's military infrastructure towards our borders -- each time confirms the nature of this alliance," President Vladimir Putin's spokesman added.

He said Russia had little contact with NATO and took no interest in a current row over spending by the 29-member alliance after Donald Trump claimed the US was "paying for 90 percent of NATO".

"What's going on there is none of our business," Peskov said.

Trump is set to meet Putin in Helsinki on July 16, following a trip to Britain.