Secretary of State John Kerry speaks during a meeting in Rome on Sunday. (Remo Casilli/Reuters)

Secretary of State John F. Kerry goes to Moscow on Tuesday to confer with Russian President Vladimir Putin, a leader who has been both a vexing antagonist in wars from Ukraine to Syria and a constructive partner in talks with countries such as Iran.

Kerry’s messages reflect the contradictory roles Moscow has played in its relations with Washington.

One goal is to tell Putin and Foreign Minister Sergei Lavrov that the United States and its allies will maintain punishing sanctions against Russia until it fully implements an agreement negotiated in the Belarusan capital in February to end the fighting in eastern Ukraine. The agreement calls for a cease-fire, a Russian troop withdrawal and the return to Kiev of full control over its eastern border. Even as the deal’s Dec. 31 deadline approaches, the Obama administration says Russia is violating it by continuing to arm, train and equip pro-Moscow rebels.

Kerry’s other, more immediate and pressing goal is to enlist Russian support in pushing a plan to end the conflict that has raged in Syria since 2011. He hopes to keep the momentum going with talks on Friday in New York, shooting for full negotiations between the government and its opponents to begin in January. And he wants Russia, which backs Syrian President Bashar al-Assad, to pressure Assad to send a representative.

“Part of this process is to have unity eventually, though we clearly do not have it now,” said a senior State Department official traveling with Kerry in Paris, where he was to meet Monday night with 10 Arab and European diplomats pushing the proposal for a transition that requires Assad to relinquish power. “How that transition will happen, the role of Assad in that transition, the secretary will go into deeper with Russian leaders on this trip.”

Russian President Vladimir Putin speaks during a meeting with Russia's Constitutional Court judges in St. Petersburg on Monday. (Mikhail Klimentyev/AFP/Getty Images)

Publicly, Kerry insists that Russia “is playing a constructive and important role” in efforts to arrange the political transition as a way out of Syria’s civil war.

He talks regularly with Lavrov, often going for long walks with him in the sprawling back yard of the U.S. ambassador’s residence in Paris. And late Monday, the Kremlin confirmed that Kerry and Putin will meet during the U.S. diplomat’s visit.

“Putin is the decision maker in Russia. It’s important to have a chance to talk to him directly,” said the State Department official, speaking on the condition of anonymity under the agency’s ground rules for talking with reporters.

Washington is frustrated with Russia’s support for Assad, even though it is one of the countries that has endorsed the transition plan, reached a few weeks ago in Vienna. The United States, its allies and most opposition groups insist that Assad must step down for the fighting to end.

To Washington’s consternation, Russian airstrikes in Syria — which Moscow began in late September — are still largely trained on rebel fighters opposed to Assad and backed by the United States and its allies, in effect propping him up rather than targeting Islamic State strongholds. The Islamic State, an al-Qaeda offshoot also known as ISIS, ISIL and Daesh, has declared a caliphate in parts of Iraq and Syria that are under its control.

“A lot of strikes continue go in the wrong direction,” the State Department official said.

Although Iran’s support for Assad appears to be steadfast, some U.S. officials and Western diplomats believe that Russia is reluctant to get more deeply involved in a military campaign in Syria and may be softening.

“In our conversations with the Russians, there is a growing recognition that Assad will not be part of the solution,” a European diplomat said.

The Obama administration is trying to make clear in its dealings with Moscow that it cannot expect sanctions imposed on Russia over its role in the Ukraine conflict to be lifted if it scales down its support for Assad.

“We have made absolutely clear on every level, from the president on down, we are not playing ‘Let’s Make a Deal,’ trading Ukraine for Syria,” the State Department official said. “These are distinct issues, with distinct paths forward.”

Yet even as Kerry was in Paris for climate change talks last week, the prospects for peace in Syria made few advances and even suffered some setbacks.

A conference in the Saudi capital, Riyadh, last week brought more than 100 opposition groups and rebels together in a bid to find agreement on a framework for peace negotiations with Damascus, including the demand that Assad must go.

Kerry said the conference was a sign of progress, but others expressed dissatisfaction. The Russian Foreign Ministry said the group was not broad enough and did not have the right to speak for the opposition as a whole. Assad, meanwhile, said he would never negotiate with opposition groups he considers “terrorists.”

Kerry’s trip to Moscow caps a whirlwind week in which he has lurched from one world crisis to another.

His six days at the climate change conference in Paris went into overtime with a last-minute cliffhanger over changing one word — “shall” to “should” — that toned down the legal obligation for reducing emission targets.

He left before dawn on Sunday for Rome to co-host a day-long conference on Libya, where Islamist extremists escaping the Syrian battlegrounds have ensconced themselves.

He returned to Paris that night for Monday’s talks on Syria, and he was scheduled to fly most of Monday night to arrive in Moscow just before dawn on Tuesday.

In between, he marked two personal milestones. He turned 72 on Friday, accepting a huge bouquet of flowers from the Indian environment minister. And he logged travel miles that pushed him past a total of 958,000, breaking Hillary Clinton’s record and putting him on track to surpass Condoleezza Rice next year to become the most traveled secretary of state in U.S. history. One way he survives his grueling schedule is by wearing compression socks while in the air.

Even for Kerry, who routinely keeps forging ahead even when his much younger staff is ready to drop, the pace of recent days was at times bewildering.

As he sat down with reporters on Saturday night at the end of the climate talks, he jokingly conflated that issue with the Islamist threat in Syria, saying he was heading off to Rome to discuss “two degrees of Daesh.”

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