Any withdrawal risks leaving the Kurds exposed to a long threatened attack by neighbouring Turkey, which views Kurdish fighters as "terrorists". "We tell those groups who are betting on the Americans that the Americans will not protect you," Assad said in a televised speech.
"The Americans do not hold you in their heart... They will put you in their pocket so you can be a bargaining chip." Apart from fighting IS, the Kurds have largely stayed out of Syria's civil war, working towards semi-autonomy in the northeast of the country.
The looming prospect of a US withdrawal, announced in December, has sent them scrambling to rebuild ties with the Damascus regime, but talks so far have failed to reach a compromise. "If you don't prepare yourselves to defend your country and resist, you will be nothing but a slave to the Ottomans," Assad warned, using a historic term for Turks.
"No one will protect you except your state. No one will defend you except the Syrian Arab army," he said. The Kurdish-led Syrian Democratic Forces, which has fought IS with backing from the US-led coalition since 2015, on Sunday met to discuss "the future of relations with the Syrian government".