UK russia
The Kremlin has slammed the talks, saying they don't bring the "slightest added value" to the war.
More of the mercenaries are gathering in Belarus, which borders several Nato members.
The highly-anticipated pushback against the Russian troops has not been as fast as Kyiv and its allies had hoped.
It comes after Poland sent troops to the border amid worries about Belarus.
It was dubbed "a remarkable moment filled with symbolism".
The UK claims Moscow's frontline forces are dealing with "attrition" and ammunition shortages.
Meanwhile Volodymyr Zelenskyy has warned the battlefield is moving into Russian territory.
One Russian newspaper wandered if "the novelty had worn off".
The foreign affairs committee said the UK underestimated the mercenaries for years.
Intelligence shared with The Washington Post shows the Russian president was warned about Yevgeny Prigozhin's plans “at least two or three days” in advance.