U.S. President Barack Obama comforts cancer patient Debby Smith of Appalachia, Virginia, during a forum on healthcare at Northern Virginia Community College in Annandale, Virginia July 1, 2009.[Agencies]

With Congress out of session for a week, Obama urged participants at a question-and-answer session in a Washington suburb to be wary of "scare tactics" and hugged a woman who said she did not have health insurance or money of her own to treat a tumor.

"You are what is going to drive this process forward. Because if Congress thinks that the American people don't want to see change, frankly, the lobbyists and the special interests will end up winning the day," Obama said at the meeting, which featured questions posed on YouTube and a parallel discussion on the White House Facebook page.

Obama has challenged Congress to send him legislation by the end of the year that will rein in rising healthcare costs and extend insurance to most of the 46 million Americans who lack it.

Obama hopes his top legislative priority will attract support from both parties, and on Tuesday received a welcome boost when Wal-Mart Stores Inc, the world's largest retailer, said it supported Obama's push to require large employers to offer healthcare insurance to workers -- a key part of the plan.