Support for the U.S. military mission in Libya and the president’s handling of the situation is declining.

A new Rasmussen Reports national telephone survey finds that 39% of Likely U.S. Voters now agree with the president’s decision to take military action in Libya, down from 45% two weeks ago just after the mission began. Nearly as many (37%) now disagree with Obama’s decision, while 24% remain undecided. (To see survey question wording, click here.)

At the same time, only 37% rate the president’s handling of the situation in Libya as good or excellent. That’s down six points from a week ago, just after the president’s nationally televised address to the nation explaining his reasons for helping Libyan rebels overthrow longtime dictator Moammar Gadhafi. Twenty-eight percent (28%) now give the president poor marks, in line with the 30% who felt that way a week ago.

Belief that Libya is a vital national security interest of the United States today, while low before, also has slipped a bit. Just 24% now believe that to be true, compared to 27% a week ago. Fifty percent (50%) say Libya is not a vital U.S. national security interest, up from 42% two weeks ago. Twenty-six percent (26%) are not sure.

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The survey of 1,000 Likely Voters was conducted on April 5-6, 2011 by Rasmussen Reports. The margin of sampling error is +/- 3 percentage points with a 95% level of confidence. Field work for all Rasmussen Reports surveys is conducted by Pulse Opinion Research, LLC. See methodology.