The Metro Board yesterday decided to buy 200 more subway cars from an Italian manufacturer that is 10 months behind on a contract to build 94 badly needed cars for the transit authority.

The decision to sign an option to spend about $160 million for the 200 additional cars came at the recommendation of Metro General Manager Richard S. Page. "In an ideal world, I would not exercise the option" until Metro had operating experience with the 94 as-yet-delivered cars, Page said.

However, he said, the opportunity to exercise the option expires in June and "we have seen enough progress by this [manufacturer] to know that we are going to get a car of extremely high quality. We believe it will be better and more reliable than the cars we have today." The price per car, about $800,000, is probably better than Metro could do by starting a new procurement, Page said.

The lack of subway cars is one of the reasons the Metro board is engaged in a fractious debate about whether to open this year three new stations and two more miles of subway -- the Red Line extension from Dupont Circle north to Van Ness-UDC, at Connecticut Avenue and Yuma Street NW.

To do so without more cars, the Metro staff told the board yesterday, would require cutting some six-car trains on the Orange Line to four cars. That cut, plus the return to service of six existing cars that have been either damaged or used for purposes other than carrying people, would give Metro enough cars to open the Van Ness extension without lengthening intervals between trains on any line, Page said.

Before yesterday, however, the board had been assuming that the first of the 94 new cars from the Italian firm, Breda Construzioni, would be available for service in May, 1982. Yesterday, Page said in a memo, he does not expect any of the new cars to be ready for service before September, but that the subway stations will be ready in December.

Therefore, the board really must decide whether to open the Van Ness extension Dec. 5, as Page formally recommended yesterday; next May, as Page had recommended when he submitted a proposed budget last December, or next September. To wait that long, Metro staffers pointed out yesterday, would be to let a usable facility lie idle. Further, they said, they believe they can operate a satisfactory but somewhat crowded railroad until the new cars arrive.

The 94 new cars already on order will cost Metro about $74 million. The first car was to have been delivered to Metro this July. However, Metro officials said, a giant aluminum-extrusion press used to form the sides of the Metro cars broke down and forced a previously announced six-month delay.

An additional four months has been added to that delay, Page said, because some of the early extruded panels did not pass quality control requirements at Breda. "I would much rather find that out now and suffer the delay today than I would find that out months or years later," Page said.

Metro experts have made quarterly visits to Florence, Italy, to monitor the car construction and have verified the problem with the aluminum press, Page said. "We think we have in Breda a very reliable supplier," he said. With the exercise of the option yesterday, the Metro board will have at least a six-year contractual relationship with Breda, extending into 1985. Breda won the original contract in competitive bidding.

When all the new cars now on order join the Metro fleet, it will total 594 cars, or six more than Metro is estimating will be needed to operate a subway system that includes:

The Red Line from Dupont Circle north to Shady Grove Road in Montgomery County.

The Blue Line from National Airport south to Huntington.

The Yellow Line between the Pentagon and Gallery Place across the 14th Street Bridge.

The Orange Line from Ballston to Vienna.

The inner-city Green Line between Anacostia and U Street NW.

By the time the Metro board began discussing the Van Ness extension proposal yesterday, it was early afternoon and board members had been meeting since 8:30 a.m. The morning sessions were filled with divisive debate over Metro's proposed 1982 budget and an arcane procedural battle over how to carve up the costs, revenues and subsidies among the eight local jurisdictions that make up the Metro coalition.

In brief, Montgomery and Prince George's counties lost in a Metro committee attempt to cut $7 million from the budget. They offered a number of amendments, each of which failed by either a 4-4 or 5-3 vote. The full Metro board cannot adopt a budget without at least one vote from Maryland, so some compromise will have to be worked out.

Next the District of Columbia, in concert with the Maryland counties, halted approval of the formula which determines how much subsidy each jurisdiction must provide to run Metro. The District wants to add an element to the formula. It would save the District some money, estimated at less than $100,000 by Metro; it would probably cost Fairfax County about the same amount. At least one vote from the District is required to pass the formula, so another compromise will have to be worked out.

Finally, when Page proposed opening the Van Ness extension and said it could be done at no extra cost in total subsidy, his staff dropped on the table a document showing that Fairfax County, for complicated reasons, would have to pay about $360,000 more, while others would pay about that much less.

"What's in this for us?" Fairfax County Supervisor Joseph Alexander asked.

That's another compromise to be worked out.