Representatives from the Washington Medical Assn., which represents doctors, say the practice, which has been allowed for more than 30 years there, has caused no problems.
This week the British Medical Association (BMA), which represents doctors, urged switching systems.
The British Medical Association, which represents doctors, described the freeze as "very disappointing news".
The British Medical Association, which represents doctors, and the main nurses' association are making noisy last-ditch protests.
The move will further inflame tensions between ministers and the British Medical Association that represents doctors.
The British Medical Association, which represents doctors, has raised concerns about the plans.
But Dr Andrew Dearden, who represents doctors in the giant NHS pension scheme, said concerns over unfunded schemes were entirely misplaced.
The American Medical Association, which represents doctors, also came out in opposition today and less surprisingly, so did private insurance companies.
The move was backed by the Royal College of Physicians, which represents the UK's 30,000 hospital doctors, and the Medical Defence Union, which represents doctors accused of wrongdoing.
But the British Medical Association, the professional association which represents doctors, warned that this could deter doctors from carrying out complex surgery or operations on frail and elderly patients.
The British Medical Association (BMA), which represents doctors, said the NHS was "struggling to cope with the sheer number of patients coming through the door".
