ANNANDALE, Va. — President Barack Obama returned to the familiar trappings of a political campaign on Wednesday, holding a town-hall-style meeting where he sought to heighten the urgency surrounding the health-care debate and dismissed critics who say the issue is too complex to tackle during his first year in office.

"Next thing you know, another 10 years has gone by and we still haven't done anything," Obama said, stopping just shy of mocking the congressional work pace. "That's not what's going to happen this time. I am going to keep on pressing until we get it done this year."

With members of Congress away for the week, the president had the stage to himself as he promoted his plan to lower the cost of health care and make coverage more accessible. He cast his proposal as a cost-saver, rather than a giant expenditure, saying the economy was not likely to rally without reversing "the crushing cost of health care."

For weeks, the administration and congressional leaders have struggled to reach a compromise on comprehensive health-care legislation. So the White House sought to rally public support by staging a friendly forum here, just outside Washington, which was billed as an hourlong question-and-answer session from a live audience, as well as from people following along online.

But 20 minutes into the meeting, Obama suddenly seemed to notice that he had been doing all of the talking and none of the listening. So before fielding his first question, he apologized for slipping into the policy details, saying, "I'm almost done here, but this is a big, complicated topic, so I hope you forgive me."

The president ultimately took seven questions, including four that had been selected by aides who waded through hundreds of videos submitted through the White House Web site. (One, though, came from a Republican congressman from Texas asking about medical malpractice.) Three questions were from members of the audience, all of whom were associated with groups close to the Democratic Party.

Asked whether a government-run, single-payer health-care system could work, Obama said no, explaining that most people are insured through employers that are private companies. But he renewed his push for a so-called public option, which could compete with private insurers and, Obama said, "keep insurers honest."