"My message to the US military command: when the battle against ISIS will end, no American soldier will be tolerated in Syria. I advise you to leave by your own will or you will be forced to it," said Soleimani to a Russian officer. Soleimani asked the Russian officer to make known the Iranian intentions towards the US: that they will be considered as forces of occupation if these decide to stay in northeast Syria where Kurds and Arab tribes cohabit together.
The Russians are not necessarily against the US presence and can adapt to this after defining the demarcation lines to avoid any clash, but Iran has a clear position and has decided not to abandon the Syrian President alone to face the US forces, if these stay behind.
Soleimani's message to the US clearly indicated the promise of 'surprise measures' against the US: "You shall face soldiers and forces you have not experienced before in Syria and you will leave the country sooner or later."
Russia conveyed to the US that Iran will stay in Syria as long as President Assad desires, and he insists on liberating the entire territory from all forces without exception. Russia confirmed to the US its intention to refrain from offering any air support to Iran and its allies in the case of attacks on US forces. From the Russian perspective, the Iran-US dispute is not its concern nor on its agenda.