US National Security Adviser John Bolton said on Tuesday that Trump was hoping to meet in Osaka with both with Putin and Chinese leader Xi Jinping.

"It is from the US side that relevant impulses must follow. If they are no [such impulses], then, as I understand, the contact [between Putin and Trump] can still take place, but it will be, as they say, 'on-the-go,'" Ryabkov said.

The deputy minister noted that Washington had not brought forward any concrete proposals so far.

"We see no concrete signals apart from what we occasionally hear from US representatives. But contacts at such a level are generally not prepared through exchanges of some verbal comments in a somewhat free-style manner," the diplomat added.