Of the millions of Americans without health insurance last year, most worked for small businesses, according to SurePayroll.

Roughly half of the nation's small employers don't provide health-care coverage, leaving up to 33 million small-business employees without insurance in 2007, the Chicago-based payroll firm estimates.

According to Census data released this week, a total of 45.7 million Americans were uninsured last year.

Without employer-provided insurance, workers are forced to seek other health-care coverage options, said SurePayroll CEO Michael Alter.

"These aren't good options unless you are healthy," he said. "People that need insurance the most are those who aren't healthy."

According to Alter, small employers are often deterred from offering health-care coverage by a range of issues, including added costs, access to brokers and a lack of industry knowledge.

Yet, in a recent survey eight out of 10 small employers ranked employee health insurance coverage as "important" or "very important," Alter added.