In light of all of the recent tensions between the US and Russia, of which there have been many (here, here, here, here, and here), one would assume that Putin wouldn't be interested in working with the US on anything other than steering clear of each other for time being.
However, as RT reports, Russia has extended an olive branch with the US. Defense Minister Sergey Shoigu recently told journalists that the US and Russia should fly joint missions together in Syria to fight ISIS.
"Taking such a step would help the progress of the peace settlement in Syria. Of course such measures have been agreed with the Syrian Arab Republic. Yesterday we started negotiating these measures with our colleagues in Oman and Geneva.
We suggest to the US, starting on May 25, joint action of the Russian Air Forces and the US-led coalition forces to plan and conduct strikes against the Al-Nusra Front, which does not support the ceasefire, as well as against convoys of arms and fighters crossing the Syrian-Turkish border."
The suggestion puts the US in a difficult situation from a legal and public relations standpoint. Washington for years has been treating Syrian President Bashar Assad as an illegitimate figure, rather than Syria’s head of state. The airstrikes it conducts in Syria are illegal because the US has neither a mandate from the UN Security Council nor an invitation from Damascus to use force in a sovereign nation’s territory.
Moscow, for its part, was called upon by the Syrian government to help its army fight against terrorist forces. Joint Russian-US missions would technically require legal permission from Damascus to Washington, and asking for one would be a great embarrassment for the Obama administration and a serious blow for the Democratic Party, which would be exposed to Republican criticism in an election year.
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Russia has clearly demonstrated that it doesn't need any help to get the job done in Syria. This is just one more opportunity for Vladimir Putin to embarrass the Obama administration on a global stage. If the US agrees, then it has to ask Assad for permission to operate in the country. If the US declines, then the world will look at it as the US turning its nose up at a chance to smooth relations with Russia and work for the common good. Either way, Putin wins again.