The two-day poll was conducted as the Obama administration weighs launching strikes against Syria for the alleged use of chemicals weapons in its violent civil war, as well as amid growing demands by U.S. lawmakers that Congress should have a voice in any debate to authorize force.
On Thursday night, the Obama administration briefed congressional leaders in its effort to make the case for military intervention.
Also on Thursday, Britain's parliament rejected a motion urging an international response to the reported use of chemical weapons in Syria.
In this new NBC poll, 50 percent of respondents oppose the United States taking military action in response to Syria's suspected use of chemical weapons, compared with 42 percent who support it.
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And 58 percent agree with the statement that the use of chemical weapons by any country violates a "red line" that requires a significant U.S. response, including the possibility of U.S. action.
Still, a whopping 79 percent of respondents—including nearly seven-in-10 Democrats and 90 percent of Republicans— say the president should be required to receive congressional approval before taking any action.
The poll also finds that only 21 percent think taking action against the Syrian government is in the United States' national interest. By comparison, 33 percent disagree and 45 percent don't know enough to have an opinion.
And just 27 percent say that U.S. military force will improve the situation for Syrian civilians, versus 41 percent who say it won't.
