In a triumph for President Barack Obama, Democrats narrowly pushed sweeping health care legislation through a key congressional committee Friday night and cleared the way for a September showdown in the House of Representatives. The 31-28 vote in the House Energy and Commerce Committee, along party lines, was weeks later than either the White House or Democratic leaders had hoped. But the vote was just one step in a lengthy legislative process that has already lagged the schedule set out by Obama. The progress in the House toward providing health care to 50 million uninsured Americans was not matched in the Senate where Republican and Democratic negotiators announced they needed additional time to produce an agreement. Overall prospects for a health bill remain uncertain. Both chambers would have to pass legislation, then work out the differences between the two versions. The United States is the only developed nation that does not have a comprehensive national health care plan for all its citizens, and Obama campaigned on a promise to offer affordable health care to all Americans. However, the recession and a deepening budget deficit have made it difficult to win support for costly new programs. Polls show many Americans fear an overhaul of the health system will reduce the quality of health care and increase costs. Republicans, battered in the last two elections, have seized on the issue, to attack Obama, whose popularity has slipped in recent weeks. The Energy and Commerce Committee was the third of three House panels to act on the legislation, a measure that numerous lawmakers note would rearrange one-sixth of the nation's economy. A vote in the full House is expected in September, after lawmakers return from a monthlong vacation. Democrats on the energy and commerce panel made an intensive effort to satisfy the conflicting demands of liberals and conservatives on the committee, unity necessary to overcome a solid wall of Republican opposition. “We have agreed we need to pull together,” said Rep. Henry Waxman, the Democratic committee chairman who presided over hours of private negotiations and public committee meetings. Five Democrats opposed the bill. While the pace of action was slower than party leaders had hoped, it was speedier by far than the timetable in the Senate. There, Democrats said a deadline of Sept. 15 had been imposed on marathon talks.