Faced with the daunting task of debugging Medicare computers before Jan. 1, 2000, the Clinton administration wants to put off scheduled increases in the payments for hospitals and doctors.

Republicans in Congress immediately seized on the plan, outlined in an internal memo, accusing the administration of backing down from agreements reached during lengthy negotiations over Medicare spending last year."I am very disappointed to hear of the administration's failure to implement Balanced Budget Act changes and its plan to delay payment updates for doctors and hospitals who care for our seniors," said Rep. Bill Thomas, R-Calif., chairman of the House Ways and Means health subcommittee. He scheduled a hearing next month to address the issue.

Medicare payments were already substantially cut in order to balance the federal budget, said Ari Fleischer, a Thomas spokesman.

"The bottom can drop out if you cut doctors and hospitals too much," he said.

Administration officials plan to brief congressional staff about the issue next week. Any changes in payments would need congressional approval.

In a memo outlining the problem, Nancy-Ann Min DeParle, administrator of the agency that runs Medicare, explained that major changes must be made to computer systems to change payment rates. But contractors are working to overhaul those same computers to prevent them from crashing on Jan. 1, 2000.

Both tasks cannot be done at the same time, she said.

Computers have been programmed to use two-digit numbers to represent years, assuming they are in the 1900s. Without being fixed, computers will read the year 2000 as 1900.

Medicare's computers are among the most troubled in the federal government. If they aren't fixed, the government will be unable to pay its bills.

A Medicare spokesman emphasized the need to keep the system running.

"We're devising the right strategy to assure, come Jan. 1, 2000, Medicare subscribers get the health care they need and Medicare providers are paid promptly," said Chris Peacock, spokesman for the Health Care Financing Administration, which runs Medicare.