Syrian President Bashar Assad vowed on Thursday to recover the country's territory held by U.S. troops, threatening to expel American forces.

"This is the first option. If not, we're going to resort to liberating those areas by force. We don't have any other options, with the Americans or without the Americans," Assad told RT in an interview.

"This is our land, it's our right, and it's our duty to liberate it. The Americans should leave, somehow they're going to leave," he continued. "They came to Iraq with no legal basis, and look what happened to them. They have to learn the lesson. Iraq is no exception, and Syria is no exception. People will not accept foreigners in this region anymore," he continued.

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Tensions between the U.S. and Damascus have ratcheted up during the Trump administration over the United States' actions in the Syria's seven-year civil war.

The U.S. joined the United Kingdom and France in airstrikes against Syria last month following a reported chemical attack on civilians. The U.S. and much of the West blamed the Assad government for the attack, which was launched in a rebel-held area.

"These are not the actions of a man; they are crimes of a monster instead,” President Trump said in an address following the attack.

The State Department last week expressed concern about an "impending" operation by Assad's forces in Syria that it says will fall inside the boundaries of a U.S.-enforced de-escalation zone.

The State Department spokeswoman Heather Nauert said Washington would respond with "firm and appropriate measures" if the Syrian government were to go against the terms of the cease-fire in the region, located in the southwestern part of the country.