WASHINGTON—The drive to enact sweeping health care reform is about to kick into high gear.

This week, at least one congressional panel—the Senate Health, Education, Labor and Pensions Committee—is set to begin debating a reform bill, while other committees also are expected to begin deliberations soon.

If congressional leaders stick to their ambitious timetables, reform legislation could be ready for consideration by the full House and Senate within about a month.

For employers, the risks and rewards posed by reform legislation are numerous.

More than likely, employers—except the smallest firms—would be required, in order to avoid financial penalties, to offer health care coverage to employees that met legislatively set standards. That could mean coverage might have to be extended to some employees, such as part-timers, who historically have been excluded from employer-sponsored plans.

It also could mean some rapidly growing plans—most notably high-deductible health insurance plans linked to health savings accounts—might not be generous enough to meet coverage standards, putting an end to an approach many employers believe offer significant potential to control costs.

In addition, legislators could agree on a reform package that includes the establishment of a public plan, which would be offered by newly established state health insurance exchanges.

President Obama stumped for the public plan option last week, arguing it is needed to give private health insurers more competition. While details of the plan are in flux, it could mean new headaches for employers if their employees are allowed to opt out of corporate plans, resulting in employers having to deal with more health plans.

Finally, legislators could agree on a reform package in which employees for the first time would be taxed on at least a portion of employer-paid coverage. For employees, that would mean a reduction in take-home pay and, for employers, it would mean a big increase in their administrative workload as they try to calculate the value of coverage.

“There is no way that your average company could do the necessary calculations on its own,” said James Gelfand, senior health care policy manager at the U.S. Chamber of Commerce in Washington.

But if the risks to employers posed by reform legislation are significant, so are the rewards. If legislation is passed and it results in near-universal health coverage, employers could benefit because providers no longer would need to shift costs of uncompensated care delivered to the uninsured to patients in insured plans.

This isn't the first time Congress has taken up comprehensive health reform care legislation.

The last major effort in 1993 collapsed for many reasons, not the least of which was the Clinton administration's failure to bring in key legislators in framing the legislation. In contrast, Congress, with support from the Obama administration, now is leading the latest reform drive, increasing the chances of passage.

At the same time, with health care costs much higher today and a smaller percentage of employers offering coverage, there is much greater public interest in revamping the health care system.

Since the last failure, “costs have risen dramatically, so have the number of uninsured. While everyone is struggling with the details, there is a consensus that there needs to be reform,” said Frank McArdle, a consultant with Hewitt Associates Inc. in Washington.

Nevertheless, the process “will not be a cakewalk,” he said. “The reason reform has taken so long is that the issues are so difficult.”

But what will be in the final bill is far from certain.

“My sense is that something will pass, but we don't know exactly what it will be,” said Michael Thompson, a principal with PricewaterhouseCoopers L.L.P. in New York.

The mood of employers is one of “nervous tension,” said Chantel Sheaks, a principal with Buck Consultants L.L.C. in Washington.

Even as congressional committees are about to act, many of the blanks remain to be filled in. For example, a 615-page bill proposed by Sens. Edward Kennedy, D-Mass., and Chris Dodd, D-Conn., that the HELP Committee will take up this week, simply says an employer mandate is “under discussion.”

The shape of any mandate is of crucial importance to employers.

“The key issue is, what would be considered minimum acceptable coverage? Would, for example, an employer have to provide coverage to part-timers or seasonal employees?” asked Ms. Sheaks.

The answers to those questions will determine the cost impact on some employers.

Another big question is whether legislators will limit the tax-free status of employer-provided coverage, in which premium payments made by employers now are excluded from employees' taxable income.

Senate Finance Committee Chairman Max Baucus, D-Mont., whose panel is expected to unveil a bill this week, said that measure may include a provision where employees in very rich plans would be taxed on costs over a certain level.

Experts, though, worry that if revenues fall short of funding a key part of reform legislation—providing insurance premium subsidies for the low-income uninsured—the so-called benefit tax cap could be lowered, affecting far more employers and employees. Putting aside the issue of whether taxing employees on health care benefits is good policy, experts say there would be difficulties in determining the value of benefits to be taxed, including issues such as whether the costs of service providers such as third-party claims administrators should be included.

“Valuation would be a huge issue,” said Gretchen Young, vp-health policy at the ERISA Industry Committee in Washington.