WASHINGTON — Amid an increasingly partisan atmosphere, the head of the Federal Aviation Administration told skeptical Republicans on Wednesday that automatic budget cuts had forced the F.A.A. to run somewhat like a starving airline: it has reduced its inventory of spare parts, stopped hiring and training new employees, and cut back on modernization.

The cuts imposed by Congress have made sharp reductions in staffing inevitable at airport control towers and radar rooms, said Michael P. Huerta, the F.A.A. administrator, speaking to the transportation subcommittee of the House Committee on Appropriations. He said that he and others at the Transportation Department had been warning since February, before the sequester took effect, that it would cause layoffs that would create air traffic delays, adding that the agency had done everything it could to limit the impact.

But Representative Harold Rogers, a Kentucky Republican who is the chairman of the Appropriations Committee, said the agency had shown “a shocking lack of management,” and suggested that the Obama administration was trying to wring maximum harm from a small budget cut.