The British Minister of Foreign Affairs worries about the growing cooperation between the Syrian Kurds (YPG) and the Russians. He is right to worry about it, because if the Syrian Kurds of YPG completely align themselves with the Russians and the Kurds of Turkey (PKK), the Americans and their allies will not be able to support them, and they will lose their most important ally against ISIS of Syria. The PKK has carried out many terrorist attacks in Turkey, and the more the YPG cooperates with the PKK and the Russians, the harder it will be for the United States to support the YPG.
Alternatively, if the Americans decide to keep supporting the Syrian Kurds, while they are aligned with Russia and the PKK, it will be like indirectly supporting Russia against Turkey, and the Americans definitely do not want that. But it will happen in practice, whether they want it or not, because the Syrian Kurds, together with the PKK, might use the American weapons against Turkey in the Eastern Turkey i.e. the Turkish Kurdistan.
The United States want the Kurds of Syria to use the weapons they provide them against the Syrian Sunni Islamists (ISIS of Syria), and not against Turkey. But how do you make sure that this is what happens in practice? It’s not that simple.
“The Kurds, the Kremlin, and the Ceasefire”, February 2016
“Britain says uneasy after evidence of Kurdish coordination with Syria and Russia”, February 2016
“Turkey calls for unconditional U.S. support against Kurdish YPG”, February 2016