War has killed more than 220,000 people and displaced millions of others since it began in 2011
Republican and Democratic US senators called on President Barack Obama on Tuesday to create and enforce humanitarian safe zones in Syria, amid international concerns about the dire conditions faced by millions of people displaced by the war.
"The staggering human displacement, killing and destruction are an affront to the civilized world and must be stopped," Republican Senators John McCain and Lindsey Graham and Democrats Richard Durbin and Tim Kaine wrote to Obama in a letter seen by Reuters.
The four-year-long war in Syria has killed more than 220,000 people and displaced millions of others.
The lawmakers urged Obama to establish one or more safe zones, with "necessary enforcement mechanisms" including air assets, and securing of the border area by Turkey.
They also asked the Obama administration to provide lawmakers with an update on efforts to alleviate the humanitarian crisis in Syria, including efforts to create and enforce safe zones with US allies.
The senators also said they were disappointed that the United States has not taken in more Syrian refugees during the conflict. The country has admitted fewer than 800.