"The situation is of course concerning," Peskov told journalists. "Russia aims to continue dialogue and efforts on the diplomatic front. We are still supporters of the JCPOA (the nuclear deal)."

He said the announcement by Iran is one of the "consequences" of the United States abandoning the landmark deal.

"Russia and President (Vladimir) Putin warned of the consequences that would be imminent after one of the countries decided to end its obligations and exit the deal," Peskov said.

Tehran said Sunday it would implement the breach of the uranium enrichment cap "in a few hours". It first announced the intention to do this in May, a year after the US unilaterally abandoned the multilateral deal.

The pact's European signatories have urged Tehran to halt its advance toward breaching the uranium cap. But Iran says it has lost patience following the reimposition of sanctions by Washington.

Iran on Sunday threatened to abandon further commitments under the landmark deal in 60 days.