Secretary of State Rex Tillerson landed in Russiaon Tuesday as dark clouds from a garbage fire hovered over Moscows Vnukovo airport. It was a visible contrast to the brighter days Tillerson has enjoyed through his longstanding business ties to Russia, but as tensions rise over Syria, this weeks visit will likely feel very different.

Tillersons trip marks the Trump administrations most direct diplomatic effort in Russia, and it puts the secretary of state in a difficult position of attempting to ease the strain between the White House and the Kremlin while also pressuring Putin to pull back on his support for Assad.

Tillerson, who as the CEO of Exxon Mobil hadfriendly ties to Russian President Vladimir Putin and his associates, is likely no longer such a welcome figure in Moscow. Since last weeks poison gas attack that killed scores of civilians in Syria, Tillerson has harshly criticized the Kremlin for supporting President Bashar Assad. His rhetoric escalated after the U.S. missile strike against Syrias Shayrat Air Base in retaliation for the massacre, saying that Russias failure to keep Assad in check is what led to his use of chemical weapons.

Russiaappears to be lividover the U.S. strike and is sticking to its initial claim that it was rebel fighters and not Assad that possessed the chemical weapons. In the days since the U.S. strike, the Kremlin has suspended a key agreement with Washington to coordinate air operations over Syria, deployed a warship to the Syrian coast and said the United States violated international law. Russia announced Monday that Putin would not meet with Tillerson during the trip.

The current climate in Moscow is far from what Tillerson is accustomed to. He met with Putin numerous times during his tenure at Exxon Mobil, including in 2011, when he flew to a Sochi resort to sign a deal with majority Russian government-owned gas company Rosneft. Tillersons standing in Russia led the Kremlin to award him an Order of Friendship in 2013, and for years he was the director of a Bahamas-based U.S.-Russian subsidiary of Exxon Mobil.

Russian mediainitially assumed that Tillerson would be a pro-Russia voice in Washington, observers say, but pundits have turned away from their praise in the months since Trumps inauguration. Russias state-run news outlets have recently subjected Tillerson, as well as Trump, to some of the same scorn that faced previous administrations.

Along with the hostile atmosphere for negotiations, Tillersons goal of persuading Russia to give up support for Assad or pressure him into negotiations is inherently difficult. The Kremlin has significant strategic interests in Syria, including its sole naval base on the Mediterranean at the port of Tartus and a means of limiting U.S. power. It has also stood by Assad even after a far deadlier sarin gas attack in 2013, as well as innumerable reports of atrocities and a near daily onslaught of barrel bombings.

[The Russians] have always known that the guy is a barbarian and hes been using these means forever, said Faysal Itani, a senior fellow at the nonpartisan Atlantic Council think tank.

They dont want him there because they like him; they want him there because they think the alternative is a threat to their interests and because they see the U.S. as a strategic adversary, Itani said.

There is little to suggest that the Kremlin is willing to change its calculus on supporting Assad, and Russia has effectively doubled down on its support since the strike on Shayrat.

I dont think Rex Tillerson or even President Trump going to Russia and telling them off is going to do the job. Weve been doing exactly that since they entered Syria in 2015, Itani said.

Tillersons statement Tuesday that the reign of the Assad family is coming to an end echoed a 2012 statement made by his predecessor, John Kerry, who said that the regimes days are numbered.Its not clear if anything has changed in the United States Syria policy that gives Tillerson reason to believe Assad is now close to losing power while on the ground the Syrian opposition is at one of its weakest points since the conflict began.

There has been mixed messaging from the White House on how far the U.S. is willing to pursue military options for Syria, but no official has directly said the White House plans a large-scale intervention. Tillerson stated over the weekend that, beyond a punitive strike to deter chemical use, there was no change to the U.S. militarys posture on Syria.

Its uncertain what measures, either conciliatory or punitive, the U.S. is willing to take to pressure Russia into giving up support for Assad and losing the regional influence that it currently has as a result of its ally. The lack of a carrot or stick large enough to shift Russian actions could mean that Tillersons visit does little to change the current state of deadlock over Syrias civil war.