"I know this will be a tough vote. I know that everybody is counting votes right now in Washington,'' he said.

"I still believe we can do what's right. I still believe we can do what's hard. The need is great. The opportunity is here.

"We are going to do something historic this weekend ... We are going to fix health care in America.''

'Healthcare challenges'

It was the fourth event Obama has held on healthcare in the last two weeks, and his last public push for the legislation that tops his domestic priority list.

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Obama pledged that many of his sweeping changes would come into effect this year.

"It's a debate that is not only about the cost of our healthcare but the character of our country, about whether we can still meet the challenges of our time, about whether we're still a nation that gives its citizens a chance to reach their dreams," he said.

According to the latest Gallup poll, only 48 per cent of Americans approve of Obama's performance in office; his lowest numbers as president. Only 45 per cent support his healthcare plan.

With polls providing a mixed picture of their attitudes, the president made clear he was willing to let voters decide in November whether healthcare should be approved or not.

With the plan at stake and the future of his presidency also in the balance, he chose to delay a scheduled trip to Indonesia and Australiato concentrate on campaigning at home.

"I am calling on Congress to pass these reforms," he said. "I'm going to sign them into law. I want some courage. I want us to do the right thing."

With more than one-third of the senate and all seats in the House of Representatives up for grabs, his fellow Democrats want to move past healthcare to focus on job creation and the economy.

It is unclear whether Nancy Pelosi, the speaker of the House, will be able to muster a bare majority of 216 Democrats to pass the plan in the House, with moderates fearing a rebellion from voters more concerned about jobs.