"Who’s violated the ceasefires in Syria again and again? The very forces that the US supports," Flounders said on Friday.
On Monday, up to 65 Syrian civilians were reported killed by a US airstrike in the town of Manbij near Aleppo.
Flounders noted that the US-led coalition against the Islamic State has violated international law by bombing hospitals and schools in Syria.
"There needs to be respect for international law, respect for the ceasefires," she said.
The most urgent action needed to prevent more civilians being killed, Flounders argued, was for the United States to stop supporting rebel groups trying to topple Syrian President Bashar Assad and to halt its air operations in the country.
"The first and foremost thing that should be done is for the United States to get out of Syria, to stop its bombing and to stop its arming, funding and training of absolutely reactionary covert forces," she stated.
The United States has been "arming and funding the extremist forces including through Saudi Arabia… The only solution for this war is for the United States to get out, to stop all of the bombing and its support of covert radical opposition groupings," she said.
The US government, Flounders explained, was arming and funding "what they call a moderate opposition, they are not moderate at all — they are not moderate in any way whatsoever — and forces of the Islamic State. So you have tens of thousands of mercenary and reactionary forces just ripping Syria apart."
The war funded and fanned by the United States had so far displaced a third of the population of Syria, Flounders noted.
"That is staggering for any country. [Washington] is determined to continue this policy until the government of Syria collapses. The Syrian people have shown great determination to resist this effort to pull their country apart," she said.
"It is a US policy to tear Syria apart in an effort to bring down the entire country and to pull it apart into created sectarian violence that had no history, had no origins within Syria itself. It is a policy coming from outside," she maintained.
The international community had to make clear that the orchestrated overthrow of a sovereign government in Syria must not be permitted, Flounders concluded.