Rex Tillerson is in Russia - but is there any way he can get Vladimir Putin on board over Syria?

Picking his way down the aircraft steps after landing in Moscow, Rex Tillerson must have wished he was still an oil man.

When he came to the Russian capital previously, it had been with a wallet full of cash to swap for the local fossil fuels - a simple transaction in which everybody wins.

Now he's come as the US secretary of state, he's got an empty billfold and a pistol he'll probably never use stuffed down the back of his pants.

He's meeting Sergei Lavrov, the Russian foreign minister, and there won't be the warm smiles that he enjoyed when Vladimir Putin personally pinned the Order of Friendship when he was the boss of ExxonMobil four years ago.

His mission now is to get Russia to withdraw support for Bashar al Assad - more than a year after Putin ordered his troops and jets to fly to the rescue of the Syrian president who was losing to rebel forces.

"I think it's also worth thinking about, Russia has really aligned itself with the Assad regime, the Iranians and Hezbollah," said Tillerson shortly before he boarded the plane for Moscow.

"Is that a long-term alliance that serves Russia's interests? Or would Russia prefer to realign with the United States, with other Western countries and Middle East countries who are seeking to resolve the Syrian crisis?"

He'd failed, alongside Boris Johnson, the British Foreign Secretary, to persuade the other G7 western democracies to put up a united front with the threat of more economic sanctions against Russia - not even a proposal to target military figures which, let's face it, would have made little difference to those singled out.

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So his only "stick" in his meetings will be the one America waved when it launched 59 Tomahawk missiles at Sharyat airfield. And the threat of further airstrikes if more chemicals are used.

He's also signalled that the US may intervene militarily elsewhere to protect innocent civilians.

But this is, perhaps literally, the nuclear option.

And Putin know it.

Taking on the Syrian regime will inevitably lead to conflict in the Middle East with Russia.

Russia is a nuclear power. Conflict between the West and Russia was avoided throughout the Cold War because of the inevitability of Mutually Assured Destruction.

MADness still prevails. So it would be insane to risk war over Syria - not now that Russia is so heavily involved, and winning.

Tillerson can only hope to appeal to Putin's desire for a place in the world.

And there is a hint that the Russian president knows his reputation has taken a knock.

"Are new strikes possible or not?" he said "We have information from various sources that similar provocations - I cannot call it anything else - are being prepared in other Syrian regions, including the southern suburbs of Damascus, where there are plans to plant some substance and then blame Syrian authorities for using it ."

He's acknowledging that the use of chemical weapons by his client regime in Damascus alienates even those who subscribe to the idea that Assad is fighting a terrorist insurrection.

So he may be susceptible to inducements to appear on the side of right in pursuit of a peaceful settlement in Syria - which is what the West says it wants to see.

The problem is that no one has the slightest clue as to how to get there and therefore Putin and his allies can be forgiven for believing, however cynical and vile it may be, that there still is a way forward by military means.