The debate over health care reform is now shifting to the U.S. Senate.

Less than two weeks after the House narrowly passed its health care overhaul, Senate Democrats are expected to soon unveil their version.

The Senate's health care reform bill is expected in the neighborhood of $900 billion over ten years. While the details of the bill have yet to fully emerge, Democrats like Tim Johnson say sweeping reform is needed. But Republicans like John Thune say meaningful reform can be achieved in smaller steps.

Senator Tim Johnson says a health care bill that would get his vote would expand coverage to more Americans, including those with pre-existing conditions, while also offering a government-sponsored public option to provide more choices in coverage.

"We're closer than ever to deliver access to quality, affordable health care to all Americans in a fiscally responsible way," Johnson said.

Johnson says a new health care bill can expand coverage without adding to the federal deficit. But Senator John Thune says the version favored by most Democrats will only raise taxes and increase premiums without improving health care.

"At the end of the day, there has to be something these health care reform proposals that actually drives costs down and there isn't anything in the Democratic proposals so far that does that," Thune said.

Thune and other Republicans favor a step-by-step approach, rather than a complete overhaul. Step one, according to Thune, would be to increase competition by allowing customers to buy health coverage from out-of-state providers.

Johnson thinks debate on the Senate floor can get underway after Thanksgiving, and a final bill can be completed by Christmas.