Leading Democrats on Sunday said they expect Congress to pass a major healthcare reform backed by President Barack Obama, but supporters may have to accept legislation that falls short on some issues.

The U.S. Senate on Monday is set to begin debate on the sweeping overhaul of the $2.5 trillion U.S. healthcare system amid growing concerns about the cost of the legislation that aims to provide medical coverage for millions of the uninsured.

We want to cover the uninsured, yes, but we don't want to do it in a way that's going to drive up the costs for folks who currently have it, said Senator Evan Bayh, one of a number of centrist Democrats whose support will be crucial to pass the overhaul in the face of solid Republican opposition.

In an interview with Fox News Sunday, Bayh said he would push to make sure the legislation is cost effective but acknowledged that not every senator will get what he wants.

I don't think we can afford to do nothing with costs going up 10, 15 percent a year, Bayh said. My objective is to try and make that alternative of doing something as positive as we possibly can, realizing that -- at the end of the day it may be just imperfect.

Howard Dean, a physician and former governor from Vermont who has been critical of some of his fellow Democrats who do not back a public health insurance option, predicted on the same news show that Obama would succeed on healthcare reform.

We're going to pass a decent health care bill that really is going to start reform, Dean said.

The U.S. House of Representatives passed its version on November 7. The Senate is set to begin debate on Monday after the legislation passed a crucial procedural vote before the week-long Thanksgiving holiday break.

Senate Majority Leader Harry Reid has no margin for error as he tries to accommodate competing views among his fellow Democrats on issues like abortion, a new government-run insurance plan and efforts to rein in costs. Democrats control 60 votes in the 100-member chamber, and Reid needs every one of them to overcome solid Republican opposition.

REPUBLICAN OPPOSITION

The stakes are high for Obama. His political standing and legislative agenda are on the line. A number of moderate Democrats oppose the proposed new government health insurance plan that would compete with private insurers. But some liberals, including independent Senator Bernie Sanders, insist the bill include a public plan, arguing that it would help contain insurance costs.

I would be very reluctant to support legislation that did not have a strong public option, Sanders said in an interview with ABC's This Week news show. I'm speaking for other senators, I'm speaking for many members of the House; we're going to fight and demand a public option and a strong one at that.

Republicans strongly oppose the public option, arguing that it would give government too big a role in healthcare and that private insurers would be unable to compete. They also argue the bill, which is paid for through tax increases and spending cuts, is too expensive. Many of the proposed spending cuts in the Medicare health program for the elderly are unlikely to go into effect, said Republican Senator Jon Kyl.

There's no way to fix this bill, Kyl told Fox News Sunday. He and other Republicans have called for less sweeping legislation that would allow insurers to sell across state lines as a way to lower insurance premiums. Currently insurance is regulated and sold at the state level, where one or two insurers can dominate the market.

(Editing by Cynthia Osterman)