Trump on Saturday said he would postpone a G7 summit he had hoped to hold next month until September or later and expand the list of invitees to include Australia, Russia, South Korea and India.

"President Putin is a supporter of dialogue in all directions but, in this case, in order to respond to such initiatives, we need to receive more information, which we unfortunately do not have," Kremlin spokesman Dmitry Peskov said on Monday.

"We don't know the details of this proposal yet; we don't know if it is official," he said, adding Moscow needed to know what might be on the agenda of the proposed meeting and its format, before responding.

Russia was expelled from what was then the G8 in 2014 when Barack Obama was US president, after Moscow annexed the Crimea region from Ukraine. Russia still holds the territory, and various G7 governments have rebuffed previous calls from Trump to readmit Moscow.

Peskov said other formats such as the G20 gave Russia a platform to discuss international issues with other countries.

"There are very comfortable and effective mechanisms for all participants for international dialogue, such as the G20, which allows the world's leading economies to discuss the most-pressing problems," he said.

Some Russian analysts believe Moscow should regard Trump's potential invitation with scepticism.

"Trump's intention to invite Putin as a guest of the #G7 makes no sense for Russia. All blame, no gain is what it'll get. This chapter should remain closed," Dmitri Trenin, director of the Carnegie Moscow Center and a former colonel in the Russian army, wrote on Sunday on Twitter.

Australian Associated Press