Navy Secretary W. Graham Claytor yesterday virtually invited Congress to add money to President Carter's defense budget to buy a new aircraft carrier.

"As Secretary of the Navy," Claytor told a symposium at the Naval War College here, "I will build with enthusiasm any kind of aircraft carrier authorized and directed to be built by law."

Carter's pending fiscal 1979 defense budget does not include any money for a new carrier. The president's five-year shipbuilding plan released Friday calls for postponing until fiscal 1980 the start of a new carrier, which would be oil-fired rather than nuclear-powered.

Claytor told the symposium that he prefers to save $1 billion by building as oil-fired, medium-sized carrier rather than another Nimitz-class nuclear giant. But here, too, he signaled his flexibility to Congress.

"If Congress wants to give us the other carrier," the secretary said of another Nimitz, "I'll build it with enthusiasm."

The important thing, he said, is "to start building another carrier of some kind in the near future."

Despite speculation that Claytor was about to break openly with the Carter administration over its shipbuilding plans through fiscal 1983, the Navy secretary declined to do so yesterday.

Asked if he thought the Carter five-year plan is adequate, Claytor would say only that he is still "considering it." He said he would give his views on the shipbuilding plan to Congress next week, adding it would be "inappropriate to discuss it now."

The austerity of Carter's five-year shipbuilding plan has stunned Navy leaders and is a shot subject here at the symposium being attended by about 1,200 people, including active-duty and retired Navy officers. The Carter plan calls for building 70 new ships in the plan drafted last year.

The Navy secretary's remarks yesterday may prompt Congress to start reworking the administration's five-year shipbuilding blueprint.

Claytor, who is first Navy secretary to have commanded warships, said a recent study entitled Sea Plan 2000 concluded that "the graduated presence of application of carrier and amphibious task forces is the best reassurance for our friends and the best deterrence for would-be enemies."

The Navy War College symposium, which runs through tomorrow, is designed to explore how the Navy fits into the national strategy.