The Kremlin said on Friday that a summit between Russian President Vladimir Putin and Ukrainian President Volodymyr Zelenskyy could only happen as a final step to seal a peace deal.
Kremlin spokesman Dmitry Peskov said that it was unlikely that such a meeting could occur by the end of August, as Ukraine has proposed.
"A summit meeting can and should put the final point on a settlement and cement the modalities and agreements worked out by experts. It is impossible to do it the other way round," Peskov told reporters.
"Is it possible to go through such a complex process in 30 days? Well, obviously, it is unlikely."
A Ukrainian delegate said after the latest brief round of peace talks between the two countries on Wednesday that Kyiv had proposed a Putin-Zelenskyy meeting in August because that would fall within the 50-day deadline that US President Donald Trump had set last week for a deal.
Trump has threatened new sanctions on Russia and buyers of its exports unless an agreement is reached by early September.
Peskov once again described the two sides' negotiating positions as "diametrically opposed".
"It is unlikely that they can be brought together overnight. This will require very complex diplomatic work," he said.

Trump backs down on Greenland tariffs, says deal framework reached
Death toll in Karachi mall fire climbs to around 50, official says
Rescuers search for survivors after landslide at New Zealand campsite
Israeli fire kills 11 Palestinians, Gaza medics say
Trump says US will not use force to acquire Greenland
