Washington says it was not informed about Ukraine’s plans ahead of its Aug 6 incursion into Kursk. The US has also said it did not take any part in the operation.

Ryabkov said that it was no longer an accusation that the US was involved but “an obvious fact.”

“Washington’s escalatory path is becoming more and more challenging,” Ryabkov said, according to Russian news agencies.

“The impression is that (US) colleagues have thrown away the remnants of common sense and believe that everything is permissible for them. Similar approaches are followed by their clientele in Kyiv.”

Ryabkov said such action could lead to serious consequences in terms of Russia’s own reaction and that Washington was aware of how Moscow could respond.

Russia has said that Western weaponry, including British tanks and US rocket systems, have been used by Ukraine in Kursk. Kyiv has confirmed using US Himars missiles to take out bridges in Kursk.

The New York Times reported that the US and Britain provided Ukraine with satellite imagery and other information about the Kursk region in the days after the Ukrainian attack.

The Times said that the intelligence was aimed at helping Ukraine keep better track of Russian reinforcements that might attack them or cut off their eventual withdrawal back to Ukraine.