The Kremlin said Thursday any British plan to send troops to Ukraine as part of a potential peacekeeping mission would be unacceptable for Russia and it was monitoring statements by British Prime Minister Keir Starmer with concern.

The British leader has said he is "ready and willing" to put U.K. troops on the ground in Ukraine as a security guarantee in the event of some sort of a ceasefire deal between Moscow and Kyiv.

Starmer is planning to present a plan to President Donald Trump to send fewer than 30,000 European servicemen to Ukraine in exchange for American protection of the troops, the Telegraph newspaper reported.

Kremlin spokesman Dmitry Peskov said the proposal was unacceptable because it would involve forces from a NATO member state and therefore have ramifications for Russia's own security.

"This causes concern for us, because we're talking about sending military contingents - about the possible, eventual sending of military contingents from NATO countries to Ukraine," Peskov told reporters in a daily briefing.

"This takes on a completely different meaning from the point of view of our security," he said. "We're monitoring this very closely."

Russia has repeatedly said it opposes having NATO troops on the ground in Ukraine, with Foreign Minister Sergei Lavrov saying this week that Moscow would view that as a "direct threat" to Russia's sovereignty, even if the troops operated there under a different flag.

Amid talks with the United States in Riyadh on Tuesday, Russia demanded NATO scrap its 2008 promise to one day give Ukraine membership of the U.S.-led alliance and dismissed the idea that NATO member forces could be keepers of the peace under a ceasefire deal.