As President Obama launches a media blitz to build public support for a military strike against the Syrian government, a new Washington Post-ABC News poll finds Americans moving in the reverse direction, with Republicans leading a growing legion in opposition.

More than twice as many Americans oppose launching airstrikes against Syria as support such action, 64 to 30 percent. Overall opposition jumped five percentage points from 59 percent in a Post-ABC poll last week, but the largest change in the survey was among Republicans. Fully 71 percent of Republicans now oppose launching airstrikes, up from 55 percent last week.

While showing little shift from last week, nearly seven in 10 independents remain opposed (69 percent), as do 55 percent of self-identified Democrats.  As in the previous survey, there is no political or demographic group in which a majority supports military action in Syria.

While few support using military force, Obama receives wide praise for seeking congressional authority to take action. A 57 percent majority approve of his decision to ask Congress for a vote.

A Senate committee passed a resolution last week supporting a more limited form of action; the latest Washington Post whip list estimates a majority of lawmakers in the House are at least leaning against military action. But even if the Congress does approve military action, that would only convince 14 percent of the public to move from opposition to support. Nearly half, 48 percent, would continue to oppose while 44 percent would support it.

A "no" vote in Congress would move sentiment in opposition from 65 percent to 76 percent, with a mere 17 percent remaining in favor of military action.

A separate Pew Research Center-USA Today poll also found wide and growing opposition to airstrikes in Syria. In that survey, opposition grew 15 points from the previous week and 30 points among Republicans, mirroring the shift in Post-ABC results. A CNN-ORC survey found 59 percent saying Congress should not pass a resolution authorizing military action, over six in 10 independents and Republicans opposing such a move.

The Post-ABC poll was conducted Sept. 4-8, 2013 on conventional and cellular phones among a random national sample of 1,020 adults. The margin of sampling error for overall results is plus or minus 3.5 percentage points.

Peyton M. Craighill contributed to this report.