WASHINGTON — Most people with job-based health insurance don't think of their benefits as a form of income. But Uncle Sam might just change that.

Senators are considering limiting — but not eliminating — the tax-free status of employer-provided health benefits to help pay for President Barack Obama's plan to provide coverage to 50 million uninsured Americans.

Employer-provided health insurance technically is considered part of workers' compensation, but unlike wages, it is not taxed. The forgone revenue to the federal government amounts to about $250 billion a year.

So even if they're lucky enough to avoid going to the doctor or hospital, and never use their job-based health insurance, some Americans could find themselves paying taxes on at least part of its value.

Senators on Tuesday held a discussion to begin grappling with how to finance guaranteed coverage, a cornerstone of Obama's plan to overhaul the health care system. Independent experts put the costs at about $1.5 trillion over 10 years.

Obama sees a world in which doctors and hospitals compete to offer quality service at lower costs, and the savings help cover the uninsured. Turning that vision into reality remains the biggest challenge for the president and his backers, because hard cash — not just ideas — is required to cover upfront costs of expanding coverage.

The final financing package is likely to include a mix of tax increases and spending cuts in federal health programs. Among the possibilities are tax increases on alcoholic beverages, tobacco products and sugary soft drinks, and restrictions on other health care-related tax breaks, such as flexible spending accounts.