WASHINGTON (CBSNewYork) — U.S. Secretary of State Rex Tillerson is in Moscow to meet with Russian officials about Syria as Russian President Vladimir Putin said he wants the United Nations to investigate last week’s chemical attack.

Speaking during the G-7 foreign ministers meeting in Italy ahead of his trip to Moscow, Tillerson said Russia must choose between embracing Syrian President Bashar al-Assad or aligning itself with the U.S. and like-minded countries.

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“Russia has really aligned itself with the Assad regime, with the Iranians and Hezbollah,” Tillerson said. “Is that a long term alliance that serves Russia’s interests or would Russia prefer to re-align with the United States, with other western countries and Middle East countries that are seeking to resolve the Syrian crisis?”

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The secretary of state said Russia failed to uphold its agreement to locate, secure and destroy Syria’s chemical weapons.

“It is unclear whether Russia failed to take this obligation seriously or if Russia has been incompetent, but the distinction doesn’t much matter to the dead,” he said. “We cannot let this happen again.”

Tillerson’s visit comes just a few days after President Donald Trump ordered a military strike on the Syrian air base where he said Assad launched the chemical weapons attack that killed more than 80 civilians last week.

“We do not want the regime’s uncontrolled stockpile of chemical weapons to fall into the hands of  ISIS or other terrorist groups who could and want to attack the united states or our allies,” he said.

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Russia has condemned the U.S. military strike, calling it an “aggression” and a “violation of international law” and has dismissed suggestions that the Syrian government was behind the attack.

“It reminds me of the events in 2003 when U.S. envoys to the Security Council were demonstrating what they said were chemical weapons found in Iraq,” Putin said Tuesday. “We have seen it all already.”

This week, the White House signaled that Trump may take further military action.

“If you gas a baby and put a barrel bomb in to kill innocent people, you will see a response from this president,” Press Secretary Sean Spicer said.

Meanwhile, Turkey’s health minister reportedly said Tuesday that autopsies on three victims of the chemical attack, who were brought in from Syria, confirmed sarin gas was used.

Other officials from the Organization for the Prohibition of Chemical Weapons and the World Health Organization took part in the autopsies.

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The Syrian government has denied involvement in the attack.