Assad said the government had "started now opening doors for negotiations" with the SDF.
The US's presence in Syria is not sanctioned under worldwide law.
He also said that Damascus had not engaged in talks over the country's southern region.
"Any interested party in Syria should understand that attacking U.S. forces or our coalition partners will be a bad policy", Director of Joint Staff Lieutenant General Kenneth McKenzie said at the Pentagon press briefing on Thursday.
The Pentagon is warning the Syrian regime to refrain from attacking US -backed forces in the country, shortly after Syrian President Bashar Assad demanded USA forces depart and threatened to launch attacks on territory held by American-backed Kurdish paramilitary units in northeast Syria.
In the RT interview, Assad responded sharply to U.S. President Donald Trump's recent description of him as an "animal", saying, "What you say is what you are".
He said: "We're going to liberate every area".
India not to support U.S. unilateral anti-Iran sanctions: deputy FM
Nevertheless, India continued to import Iranian crude oil and was among the last six customers of the Persian Gulf nation. The 2015 agreement between Iran and world powers lifted global sanctions on Tehran .
In return, Russian Federation is expecting Israel to provide them with assistance in restoring diplomatic ties with the United States.
The threats come amid a scramble among several nations and factions in the Syrian civil war, as the Assad government consolidates control of the major cities but faces pressure over the postwar balance of power.
The SDF wants a "democratic system based on diversity, equality, freedom, and justice" for all the country's ethnic and religious groups, he said in a voice message to Reuters.
Senior officials from Iran and Syria claimed Saturday there is no Iranian military presence in the country, amid reports that Israel and Russian Federation reached an agreement for the withdrawal of Iran-backed troops from the Israeli-Syrian border area.
Scores of Iranian soldiers have been killed in battles with insurgents in Syria, including a number of officers.
The British based Syrian Observatory for Human Rights, which looks over developments in the war, said Iranian advisers and allied Hezbollah fighters are preparing to leave the area.
Israel has been pushing Russian Federation on this issue for a while, and had conditioned not interfering in Syria's offensive against rebels in southern Syria on getting Iran, along with Shi'ite militias, out of the border region.