President Barack Obama says he expects a tough vote this weekend, but that Democrats are poised to make history when the House of Representatives votes on his healthcare reform bill.

Addressing an audience at George Mason University in Virginia, Mr Obama offered a stern warning.

"If this vote fails, the insurance industry will continue to run amok. They will continue to deny people coverage. They will continue to deny people care. They will continue to jack up premiums 40 per cent or 50 per cent or 60 per cent as they have in the last few weeks," he said.

After more than a year of intense debate, the House is expected to vote on Sunday on the sweeping healthcare overhaul, intended to extend insurance coverage to 32 million uninsured Americans.

The bill has faced solid Republican opposition, and Obama and his fellow Democrats are struggling to get enough votes from Democrats, who hold a majority of seats in both houses of Congress, to ensure its passage.

Republicans say the bill is too expensive at a time when the country is running massive budget deficits and represents an unwarranted government intrusion into Americans' relationship with their healthcare providers.