Doctors dodged yet another bullet last night as the U.S. Senate agreed to delay a scheduled 21-percent cut in Medicare payments to physicians.

But their relief will be short-lived. The delay lasts only 30 days. Doctors will have to win yet another vote before then to avoid the cuts, which apply to seniors covered by the federal Medicare health insurance program.

That cut is demanded by a formula instituted in 1997. But nearly every time the formula has called for a cut, Congress has suspended it.

The Senate was trying to pass a 30-day suspension on Friday, but the bill that included the provision was held up by retiring GOP Sen. Jim Bunning of Kentucky. He said the bill’s extra spending was not offset by new revenue. The bill that passed Tuesday night will apply retroactively to any Medicare patients seen by doctors since Monday.

For their part, doctors renewed their threat to stop seeing Medicare patients if the scheduled cut is allowed to go through. They also reiterated their calls for permanent repeal of the 1997 formula. Such a repeal was part of the health reform bills in Congress last year, but it was stripped out because it would increase the federal budget deficit by more than $200 million over 10 years.