US Ambassador to the UN Kelly Craft told the Security Council on Tuesday that Washington would implement the measures to "prevent the Assad regime from securing a military victory."
"Our aim is to deprive the Assad regime of the revenue and the support it has used to commit the large-scale atrocities and human rights violations that prevent a political resolution and severely diminish the prospects for peace," Craft said.
Russia and China criticized the US plan to impose further unilateral sanctions. Russia's UN Ambassador Vassily Nebenzia said the United States had confirmed "that the purpose of these measures is to overthrow the legitimate authorities of Syria."
China's UN Ambassador Zhang Jun said that "as vulnerable countries like Syria are struggling with the (coronavirus) pandemic, imposing more sanctions is simply inhumane and may cause additional catastrophes."
Craft said the sanctions would be imposed under the Caesar Syria Civilian Protection Act - signed by President Donald Trump in December - which aims to deter "bad actors who continue to aid and finance the Assad regime's atrocities against the Syrian people while simply enriching themselves."
Addressing a separate meeting of the Geneva-based UN Human Rights Council on Tuesday, Syria’s UN Ambassador Bashar Ja’afari, accused Washington of trying to impose U.S. law on the world and flouting calls for it to end unilateral sanctions.
A crackdown by Assad on pro-democracy protesters in 2011 led to civil war, with Moscow backing Assad and Washington supporting the opposition. Millions of people have fled Syria and millions are internally displaced.
UN Syria mediator Geir Pedersen told the Security Council he hoped to convene opposing sides in Syria's civil war in Geneva for negotiations on the constitution toward the end of August. The constitutional committee negotiations struggled to make headway last year.