WASHINGTON — President Barack Obama, citing new government data showing that nearly half of all Americans live without health insurance in a 10-year period, says the situation will only worsen without the overhaul legislation he wants Congress to send him.

Obama was to test his message — that losing health insurance can happen to anyone — at a rally Saturday in Minneapolis. A new Treasury Department analysis found that 48 percent of all Americans under age 65 go without health coverage at some point over 10 years. The data came from a study that tracked the insurance status of a sample of Americans from 1997-2006.

The report also found that more than half, or 57 percent, of people under age 21 will find themselves without insurance at some point during a span of 10 years and that more than one-third of Americans will be without coverage for a year or more.

"I refuse to allow that future to happen," Obama said in his weekly radio and Internet message. "In the United States of America, no one should have to worry that they'll go without health insurance — not for one year, not for one month, not for one day.

"And once I sign my health reform plan into law, they won't," he added.