Amid questions about Russia’s role in Syria’s chemical attack, Secretary of State Rex Tillerson met with Russian President Vladimir Putin and other officials Wednesday. While the White House has accused Moscow of helping Syrian President Bashar al-Assad’s regime of perpetuating faulty claims about the nature of the attack, one national security expert told CBS News that Putin isn’t necessarily concerned about keeping Assad in power.

Fran Townsend, former homeland security adviser to President George W. Bush and CBS News senior national security analyst, said that the Russian leader is most interested in the city of Tartus, the Russian navy’s only foothold in the Mediterranean.

“Let’s be honest. What he cares about is the strategic asset that is Tartus. That is the deep-water port on the Mediterranean, his only one, and that’s what Putin cares about,” Townsend said.

Townsend said she thinks if you could guarantee Putin’s access to the port in Tartus without Assad, it could be used as leverage over the Syrian dictator who is accused of using sarin gas on his own people.

According to CBS News correspondent Margaret Brennan, Putin, who said Wednesday that U.S.-Russia relations have “degraded” since Mr. Trump took office, stood by claims that Assad’s government was framed for the chemical weapons attack which, last week, prompted a U.S. missile barrage on a Syrian airbase.

“I think Russia’s doubled down because of course, they failed to be the guarantor that they told the Obama administration they would be. And there’s got to be real concern in the White House,” Townsend said. “This is not the only stockpile and they said as much in the declassification yesterday, they assume that there are additional chemical weapons. They’ve sent the message, the missile strike was this sort of a first step but it’s not a strategy, and so what Rex Tillerson and the administration have to do now is build strategy with coalition partners. To the extent we allow this to be a U.S.-Russia problem, we diminish our leverage, right? We would have to bring in our Arab partners who want to see Assad go to increase the pressure on Russia.”