A spokesman for the White House National Security Council declined to comment when contacted by Reuters.
Earlier this month, the United States imposed new sanctions on Russia for cyber activities against seven people, including six Russians and one Ukrainian, after which Russia imposed a retaliatory ban on 77 US citizens.
Russia accuses kyiv of planning a nuclear incident
For its part, Russia said Ukraine plans to stage a nuclear incident on its territory to blame Moscow before a United Nations meeting, without providing any evidence for the accusation.
Since the start of its invasion of Ukraine nearly a year ago, Russia has repeatedly accused Kiev of planning “false flag” operations with unconventional weapons, using biological or radioactive materials. No such attack has materialized.
The Russian Defense Ministry said in a statement that radioactive substances had been transported to Ukraine from a European country and that kyiv was preparing a large-scale “provocation”.
“The aim of the provocation is to accuse the Russian Army of allegedly carrying out indiscriminate attacks against dangerous radioactive facilities in Ukraine, causing the leakage of radioactive substances and contamination of the area,” he said.
Ukraine and its allies have dismissed such accusations as cynical attempts to spread disinformation and have accused Moscow of planning incidents of its own in an attempt to place the blame on Ukraine.