President Clinton and his economic advisers spent 18 months secretly discussing the elements of a plan to add individual investment accounts to Social Security, but abandoned it when it became clear the president would be impeached, according to a paper by three former administration officials that will be presented today at a Harvard conference.

Many of the options seriously considered by the Clinton White House include portions of the broad plan put forth by President Bush to give workers the option of private accounts. The paper makes it clear that Clinton's advisers considered objections now being made by some Democrats about Bush's approach, including risks from investing in stocks and the possibility that administrative fees would eat away potential returns, but decided the advantages of personal accounts outweighed the drawbacks.

In order to get a new system up and running before Clinton left office, the paper says, "serious consideration was given to starting the process of setting up the administrative structure for the accounts right away, a year before there was any chance of a full plan being enacted by Congress so as to shave a year off the time between enactment and having accounts set up."

While Clinton at the time indicated he was open to various approaches to overhauling Social Security, the depth of the administration's interest in private accounts was previously unknown. Bush administration officials yesterday seized on the paper to say there is a consensus in both parties that private accounts are viable.

Throughout 1998, a working group met once or twice a week, with the agenda disguised on official schedules, to discuss options and hash out details of a proposal. The president was briefed every six weeks. While Bush has appointed a commission to study the issue, the paper says that the Clinton team considered aspects of a plan in mind-numbing detail. Officials, for instance, determined how many digits to assign to the ID number for fund investments and how many key strokes would thus be required by Internal Revenue Service workers to enter all of the ID numbers each year.

Political considerations were also important. "The economic team was extremely concerned that a Social Security reform plan involving modest individual accounts might lead to total privatization in the long run," the paper says, with officials disagreeing over the best way to reach a bipartisan agreement.

The paper was written by Douglas W. Elmendorf, a deputy assistant treasury secretary; Jeffrey B. Liebman, an aide on the National Economic Council; and David W. Wilcox, an assistant treasury secretary. It will be presented at a conference examining the legacy of Clinton's economic policy.

"The administration really took seriously all the options, including individual accounts," Liebman said yesterday. He said administration officials presented Clinton with four options for revamping Social Security, but the White House was not moving toward diverting some payroll taxes to private accounts, as many Bush officials prefer. "It is impossible to know what choice the president would have made under different circumstances," Liebman said, referring to impeachment.

Clinton officials, worried by estimates that individuals could lose as much as 20 percent of retirement accounts to administrative costs, closely studied the issue. But they determined the system could be run at an annual cost of $20 to $30 an account, if costs were minimized. For instance, people would not have a choice of investments until the account value reached a minimum size, such as $5,000; account statements would be mailed once a year; and telephone inquiries would not be toll-free.

But officials also feared that the push for cost savings would make Social Security accounts appear less desirable than private plans. The paper quotes former treasury secretary Lawrence H. Summers as saying they had to guard against setting up the Post Office when people were used to dealing with Federal Express.