US senators are preparing to vote on the final Senate version of a historic healthcare reform bill. The legislation aims to cover 31 million uninsured Americans and could lead to the biggest change in US healthcare in decades. President Barack Obama said the process had been "difficult" but that the final bill was "greatly worthy of support". If approved, it would still have to be reconciled with a more expansive bill passed by the House of Representatives. Opposition Republicans say the Senate bill is expensive, authoritarian and a threat to civil liberties. Senators are due to vote on the bill at 0700 Washington time (1200GMT) on Thursday and correspondents say it is almost certain to be passed. Healthcare reform has been the key domestic policy of Mr Obama's administration but finalising the details of the proposed bills has been a lengthy and complex process. On Wednesday, the bill passed the last of three procedural votes in the Senate, with Democrats collecting the 60 votes needed to bring an end to Republican delaying tactics. Mr Obama said he was determined to "close the deal" soon. "Right now there are families who don't have health insurance and as a consequence of somebody getting sick in their family have been bankrupt," he told PBS's Newshour programme. Democrat Senate leader Harry Reid said the debate over the bill had been "a long, hard road". "We stand a few short steps from the most significant finish line we've had in Congress for many decades," he said. Republican senators have refused to back the bill and Senator Orin Hatch described it as " horrendous" and a vote-winning tactic. "It has over $500bn [£313bn] in new taxes. It gives subsidies to people who make $88,000. I mean my gosh when does it stop?" he said. "It doesn't take much to figure out that they are not as interested in healthcare as they are in maintaining control of the United States Congress." 'Frustrations' Mr Obama has had to make significant compromises to the bill to ensure its passage through the Senate. The most significant of these was to drop a government-run insurance scheme, known as the public option. But the president denied he had made too many compromises, saying the bill included "95%" of what he had hoped for. He said many of those who thought he had been too flexible were "frustrated because they haven't got what they want". "I have been very consistent throughout this process in terms of what I think is achievable and what would be good for American families," said Mr Obama. He said he would be working hard to reconcile the House and Senate bills as soon as possible, "because the American people need it now". Under the Senate bill, most Americans would have to have health insurance. Private insurers would be banned from refusing to provide insurance because applicants had pre-existing medical conditions. The House version still includes a public option and also differs on how to pay for the reform. Source: BBC