House Transportation appropriations subcommittee Chairman Robert B. Duncan (D-Ore.) warned yesterday that Congress would be increasingly reluctant to appropriate money to build more of the Metro subway until Washington area governments guarantee that they will pay the transit system's operating deficit.

Duncan made that statement during a brisk exchange with Metro General Manager Theodore C. Lutz, who was seeking to convince Duncan's subcommittee that the Carter administration budget does not propose enough money to keep Metro's construction program on schedule.

Lutz said that Metro's operating deficit, which is budgeted at $120 million for bus and subway combined in fiscal 1980, would be "billed" to local governments. He admitted that the local governments had no legal obligation to pay. "If they don't pay, what do I do, throw tangerines?" Lutz asked.

"No you don't," Duncan said. "You come down here to the prime target, the federal gevernment" to seek more federal assistance... Local governments have to be aware that there will be growing reluctance to finance the capital costs of Metro until they work out some reasonable guarantee to pay the operating costs."

"It's the only leverage we have," said Rep. William Lehmann (D-Fla.).

Duncan asked Lutz if he though Metro should have regionwide taxing authority, rather than be so dependent on the good will of local governments.

"Yes," Lutz said, "if it can be done to insure that there is still enough outside pressure (on Metro) to be a cost-effective manager."

Lutz said later he did not think it realistic to expect that the governmental obstacles to a regionwide tax could be solved.Such a solution would require the concurrence of the District of Columbia City Council, Congress, and the legislatures of Maryland and Virginia.

Recognizing that problem, Lutz has been supporting separate tax sources earmarked for Metro in each of three major jurisdictions. He predicted that, in time, both Maryland and Virginia would adopt dedicated taxes for Metro.

Lutz said that the president's budget, which includes $275 million in construction aid for fiscal 1979, fiscal 1980 and fiscal 1981, leaves the transit authority $125 million short each year of what it needs to maintain its construction schedule. The long-term result would mean, he said, that Metro would cost $300 million more than the $7 billion presently estimated and would be completed in 1990 instead of 1987.

Lutz also asked the committee to restore $150 million in fiscal 1978 construction money tht was appropriated for Metro, but that Metro was unable to spend while it was participating in a federally ordered restudy of uncompleted subway lines.

Subcommittee members questioned Lutz about everything from farecards to escalators, but spent almost 30 minutes asking why Metro did not run for three days during The Great Snowstorm.

"Perhaps we didn't take our own importance seriously enough," Lutz said. "Ixpenditures (for snow removal equipment) that three or four years ago would have gotten us the golden fleece award may now be possible to make."