In that mild rebuke of protectionism lingers the essence of the administration's nascent trade policy: conditional, ambiguous and not particularly reassuring.

The agency, the Centers for Medicare and Medicaid Services, is the largest buyer of health care in the United States. Its programs are at the heart of efforts to overhaul the health care system. If it had an administrator, that person would be working with Congress on legislation and could be preparing the agency for a new, expanded role.

“The vacancy stands out like a sore thumb,” said Dr. Denis A. Cortese, president of the Mayo Clinic, often cited by the White House as a health care model.

“In effect,” Dr. Cortese said, “Medicare is the nation’s largest insurance company. The president and Congress function as the board of directors.

“Under a strong administrator, it could take the lead in making major changes in the health care delivery system, so we’d get better outcomes and better service at lower cost.”