US president Barack Obama sought to assure Democrats he would not abandon his commitment to overhauling health care and would work to counter Republican challenges to his party's congressional dominance.

At its winter meeting, a defiant Democratic Party worked to project a message of strength even as loyalists acknowledged the prospect of several defeats in November.

The party that controls the White House typically loses seats during midterm elections at an average rate of 28 net seats. President Bill Clinton, the last Democratic commander in chief, lost control of Congress in his first term and some Democrats are believed to be predicting it could happen again.

Mr Obama warned fellow Democrats that "we have to acknowledge that change can't come quickly enough" and said political leaders must plot their way forward to November with an understanding of the economic difficulties Americans face.

"I understand their frustration. You understand it as well," the president said.

A government report on yesterday said 9.7% of the country was unemployed. Distrust of Washington has grown and spurred an anti-Washington sentiment that sent scores of activists to a "tea party" convention in Nashville on the same day.

Republican Senator Scott Brown won a special election to take the seat of the late, liberal Senator Ted Kennedy, in Massachusetts. Democrats also lost gubernatorial contests in Virginia and New Jersey.

Obama sought to energise his base against what he called "the other party" - but he also urged Democrats to work with their Republican counterparts.

While Republicans have stood in solid opposition to the president's proposed overhaul of health care, Mr Obama insisted he wasn't willing to abandon his top domestic priority that consumed months of his agenda and has produced slim hints of victory.

Mr Obama said: "Let me be clear: I am not going to walk away from health reform. We can't return to the dereliction of dut. America can't afford to wait, and we can't look backward."