President Carter, seeking to diffuse some of the political pressure over the plight of U.S. steel makers, has invited industry and congressional leaders to a private meeting at the White House next week to talk over their differences with the administration.

The unusual session, scheduled for next Thursday, is expected to include an estimated 30 to 40 steel company executives, labor leaders and members of the congressional "steel caucus." Officials said the meeting could run long as three hours.

The group will meet with top administration economic officials, including Treasury Secretary W. Michael Blumenthal, top economic adviser Charles L. Schultze, and Special Trade Representative Robert S. Strauss.

Carter himself is expected to put in a brief appearance.

Officials said the administration does not plan to unveil any new proposals affecting the industry. A special steel task force under Anthony M. Solomon, undersecretary of the Treasury for monetary affairs is working on an administration package, but is not expected to be ready then.

The move was suggested by Strauss, in part as a way to help ease the pressure placed on the White House by the industry and key congressmen. The lawmakers have become concerned by the spate of steel-industry layoffs recently, and are calling for new quotas and tax breaks.

Officials said the White House also hoped to be able to "sharpen the focus" on what steps would be realistic. Although soem congressmen have proposed specific relief measures for the industry, the steel makers themselves are divided over what should be done.

Meanwhile, the Treasury was expected to announce today it is postponing for another three months a decision on a dumping complaint involving $11 million in imports of stainless steel pipe and tubing which had been scheduled to be completed by now.

And, separately, another major U.S. steel producer announced a fall-off in profits as a result of the sales slump. The U.S. Steel Corp. said in Pittsburgh it now expects to report a drop in profits this quater and for the year as a whole.

The White House has been resisting industry demands for new import quotas, in part because policy makers fear it could upset the current multilateral trade negotiations now getting underway seriously in Geneva. The administration is trying to arrange for worldwide talks on the steel issue.

The administration also believes that not all the industry's problems are the result of competition from imports. Schultze reiterated on Tuesday that much of steel maker's current troubles stem from the impact of the recent recession and the failure to modernize their plants.

The administration and the industry also have been at odds over steel companies' pricing pratices. Steel makers have raised their prices an average 12 per cent over the past year - a jump the White House says was not justified by costs or demand.