Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE met Tuesday afternoon with Russia's ambassador to the U.S., Anatoly Antonov, amid heightened tensions involving the two nations.

State Department spokesman Heather Nauert said that Tillerson and the ambassador "discussed the need to restore Ukraine's territorial integrity and fully implement the Minsk agreements," referring to the failed cease-fire agreements between the two countries.

"The two also discussed the defeat of ISIS in Syria and the United States’s continued commitment to the Geneva talks as the best path toward a political solution to the conflict. Other topics included countering the threat posed by North Korea and the prospects for improving our bilateral relationship," she said.

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Tillerson regularly meets with foreign officials, but his meeting with the Russian envoy comes a day after special counsel Robert Mueller announced charges against three former Trump campaign officials as part of the federal probe into the campaign's ties to Russia during the 2016 election.

Mueller indicted former Trump campaign chairman Paul Manafort on nine criminal counts, including money laundering and tax fraud, while announcing that former Trump aide George Papadopoulos had pleaded guilty to lying to federal investigators about his contacts with Russians.

Trump, who has long denied that his campaign colluded with Russia during the election, greeted Antonov during a White House meeting in September. The Russian diplomat later praised the president, saying he was "warm and friendly."

Tillerson's meeting on Tuesday focused beyond the relationship between Washington and Moscow, touching on a number of issues affecting the U.S. and Russia, including the escalating threat from North Korea and the battle against the Islamic State in Iraq and Syria.

Russian President Vladimir Putin has warned the U.S. against excessive sanctioning on North Korea, saying that it might be "counterproductive" to try to decimate its economy. Meanwhile, a September ceasefire in Ukraine, offered unilaterally by separatist leaders, failed after just over a week.