Hours ahead of his first scheduled trip to Moscow, U.S. Secretary of State Rex Tillerson said it was clear that “the reign of the Assad family is coming to an end,” CBS News correspondent Margaret Brennan reports.

“But the question of how that ends and the transition itself could be very important in our view to the durability, the stability inside of a unified Syria. That’s why we are not presupposing how that occurs,” Tillerson said.

Tillerson called out Russia for continuing to prop up Syrian dictator Bashar al-Assad.

“I think it’s also worth thinking about [how] Russia has really aligned itself with the Assad regime. Is that a long term alliance that serves Russia’s interests?” he said, suggesting Russia could forge closer ties with the U.S. and other likeminded countries rather than Assad, Iran, and the militant group Hezbollah.

His comments came after the White House this week also warned that President Donald Trump could take further military action regarding Syria, Brennan reports.

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

The Kremlin condemned U.S. military strikes against Syrian regime targets, which were launched in retaliation for a chemical attack that left more than 80 civilians dead. It said that they damaged already fragile U.S.-Russian relations.

President Trump had made a campaign promise to improve relations with Russia, and the U.S. administration’s change in rhetoric regarding the country was striking, Brennan says. Over the weekend, Secretary Tillerson accused Russia of being “complicit or incompetent” in preventing the Sarin gas attack.

“I do not believe that the Russians want to have a worsening relationship with the U.S.,” Tillerson said in a TV interview on Sunday.

“But it’s going to take a lot of discussion and a lot of dialogue to better understand what is the relationship that Russia wishes to have with the U.S.,” he continued.

On his trip to Moscow, Tillerson was expected to urge Russia to stop propping up Assad, prevent further use of chemical weapons, and raise concerns about election meddling, Brennan reports.

As a former oil executive, he gained extensive experience in Russia; President Vladimir Putin once awarded him the Order of Friendship.

But now that he’s America’s top diplomat, that only goes so far, Brennan says. The U.S. strikes may complicate achieving his goals, and Russia may face new problems as well.

“It has become even more difficult for Trump, but it is now even more difficult for Putin as well, because he has to show he is a strong leader and that he will not yield under the U.S. pressure,” Russian International Affairs Council Director Andrey Kortunov told CBS News.