MOSCOW - Russian President Vladimir Putin remained open to contacts with US President Donald Trump, Kremlin spokesman Dmitry Peskov said on Monday.

A telephone conversation between Putin and Trump is not scheduled yet, Peskov said, adding that "such contacts can be agreed upon very quickly if necessary."

He noted that Russia and the United States were working on implementing ideas related to the Ukrainian settlement, but there were no specifics yet.

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In a phone interview with NBC News on Sunday, Trump said he was "very angry" and "pissed off" when Putin criticized the credibility of Ukrainian President Volodymyr Zelensky's leadership, adding that the comments were "not going in the right location."

Trump said Putin knows he is angry, but he has "a very good relationship" with Putin and would speak to the Russian leader again.

Meanwhile, the Russian Defense Ministry said on Monday that Ukraine continued to strike Russia's energy facilities on Sunday despite a previous ceasefire agreement.

An artillery shelling and a drone attack, both targeting facilities of an electricity operator in the border region of Bryansk, were registered, the ministry said in a statement, adding that both strikes caused power cuts to local households.

The attacks demonstrated "the complete inability" of Ukraine to agree on any of its obligations on the conflict settlement, the ministry said.

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In recent days, Russia and Ukraine have accused each other of violating a 30-day ceasefire on energy infrastructure.

Ukraine previously said Russia had struck its energy facility in the southern city of Kherson and called on the United States to react, according to media reports.