The American Medical Association will launch a multimillion-dollar ad campaign aimed at prodding lawmakers to rescind a 21 percent cut in Medicare physician payments that went into effect Tuesday.

Congress left town last week for the Memorial Day recess without completing work on legislation that would have delayed the scheduled payment cut. While the House approved a bill forestalling the reduction for 19 months, the Senate is not expected to consider the measure until it returns next week.

AMA President J. James Rohack blasted the Senate for leaving town with unfinished business at hand.

“Senators need to hear from people in their home states to avoid a health care crisis caused by the Senate’s inability to take action on this critical issue,” Rohack said in a statement. “The AMA will not sit silent while Senate inaction guts Medicare’s physician foundation.”

In his statement, Rohack added that during a telephone news conference scheduled for Thursday, he will unveil “details of a brand-new multi-million dollar AMA ad campaign and share results of our latest physician survey on the Medicare cut’s impact on patients.” He said the ad campaign will urge Americans to call their Senators “to help avoid a Medicare meltdown.”

The AMA has one of the best-funded lobbying operations in Washington, D.C., spending $6.1 million on lobbying in the first quarter of this year, according to disclosure filings with Congress. The doctors group helped push through the ambitious health care overhaul signed by President Barack Obama earlier this year. However, it has had less success in persuading Congress to permanently revamp the Medicare formula that determines physician reimbursement rates.

A number of fiscally conservative lawmakers, particularly in the Senate, have insisted that the costs of dealing with what is known as the “doc fix” be offset with revenue raisers.

The House had considered a five-year fix for the physician reimbursement problem, but to address concerns from some lawmakers, it scaled back the plan to three and a half years and then to 19 months.

The House bill provides for an increase of 2.2 percentage points in physician payments for the remainder of this year and a 1 percentage point increase for next year.