The Syrian government said that Washington's recognition Monday of Israeli claims over the Golan Heights were a blatant attack on its sovereignty.
US President Donald Trump on Monday signed a proclamation recognising Israeli sovereignty over the disputed Golan Heights, a border area seized from Syria in 1967.
Israeli Prime Minister Benjamin Netanyahu called the recognition "historic" and said the Golan Heights, which are still claimed by Syria, would remain permanently under Israeli control.
The move, which breaks with decades of international consensus, drew criticism from the Syrian government.
"In a blatant attack on the sovereignty and territorial integrity of Syria, the president of the US has recognised the annexation of the Syrian Golan," a foreign ministry source said, according to state news agency SANA.
"Trump does not have the right and the legal authority to legitimise the occupation," he said.
The unnamed source also said the unlimited support the United States gives to Israel makes Washington the prime enemy of the Arabs, according to SANA.
Foreign Minister Walid Muallem also denounced the move, telling Syria TV that Trump's Golan move will isolate the US.
Syria's opposition chief Nasr al-Hariri said Trump's decision will have negative implications on the region.
"It will lead to more violence and instability and it will have negative effects on efforts to engineer peace in the region," he said on Twitter.
Russia on Monday warned of a "new wave" of tensions in the Middle East after the US Golan move.