Most Americans are not convinced that small changes will be enough to ensure Social Security's survival, a new poll finds.

President Clinton, at a town meeting last week in Kansas City, Mo., said he believes it will not take a drastic overhaul to mend the retirement program for millions of baby boomers.Only 30 percent of the public agrees, according to a survey released Thursday by the Americans Discuss Social Security project, a co-sponsor of that meeting.

More than half, 57 percent, say "big changes" are needed, with those under age 65 most convinced, according to the poll, which was conducted before the town meeting in Kansas City.

"People's perception of the crisis is actually more exaggerated than the reality of the crisis," said Carolyn Lukensmeyer, executive director of Americans Discuss Social Security.

Consensus among lawmakers and outside experts is that even without change, Social Security will have enough cash for about 30 years and then will still be able to pay 75 percent of benefits owed to retirees.

A third of Americans, though, believe that Social Security will be completely broke in 20 years, the poll says. An additional 37 percent think that in two decades the program will have only enough money to pay half the benefits owed.

Contributing to pessimism may be the belief by nearly eight in 10 people that government borrowing from Social Security's cash reserves could cause the retirement program trouble.

That money, plus interest, will in fact be needed by Social Security starting in 2012.

The telephone poll of 1,202 adults was conducted March 13-22 - about two weeks before Clinton used the Kansas City event to kick off the series of four town meetings on Social Security planned for this year. The poll's margin of error is plus or minus 3 percent.