As many as 400 of the Washington area's roughly 2,000 service stations may be forced by curtailed supplies of gasoline to close on Sundays by the end of this month, industry sources estimate.

Hundreds of others may have to shorten their hours of operation during the week or close during other days of the week, the sources estimate.

A survey of 14 oil companies supplying more than 1,400 stations here showed at week's end that 10 of them have already curtailed or have announced curtailments of between 3 and 8 percent of supplies.

These 10 companies -- Saell, Amoco, Cities Service, Texaco, Sunoco, Mobil, Phillips, Chevron, Arco and Crown -- supply more than 300 stations here, mostly under their own brand names.

So far the only major companies in the Washington market to continue supplying their dealers with all the dealers can sell is Exxon, with 450 stations here, and Gulf, with 150.

Nobody knows how long that can last. Customers have switched to Exxon in such numbers because of its plentiful supplies and low prices that its demand for three recent months has soared 15 percent over a year ago.

Demand industrywide has gone up about 3 percent.

An Exxon spokesman in Houston said late last week that, "Supply capability is being continually assessed. ... If the increase in demand continues to accelerate, actions will be taken that may be necessary to assure that available supplies are equitably distributed..."

Curtailments by Exxon would hit harder in the Washington area than nationwide, industry sources say, because Exxon has about 20 percent of the gasoline market here. Nationwide it has only slightly more than 8 percent.

The curtailments are due to world-wide crude oil shortages brought on by the Iranian turmoil, but also by refinery shutdowns in the U.S.

Cities Service and BP, for example, both said they have or will soon shut down refineries for repairs.

The shortage, now estimated to have cut petroleum deliveries to the United States by an estimated 2 1/2 percent, has driven oil prices up here and around the world.

Spokesmen for several oil companies said another reason that supplies to gasoline dealers are now being curtailed is that the companies are trying to build up their inventories of fuel.

"We're trying to build our inventory so that we have a large inventory for the (spring and summer) driving season," said a Texaco executive.

Shell, the largest supplier of jet fuel in the nation, announced Friday a nationwide curtailment of that product, Cities Service and Texaco had already somewhat curtailed supplies of jet fuel.

Shell will supply jet fuel at the level it did a year ago on a monthly basis -- but no more, it announced.

"We have adequate supplies through the weekend," a spokesman for Eastern Airlines said on Friday in the wake of the Shell announcement. "It looks like we won't have to alter our schedule for a while.... We'll take another look at it come Monday."

Industry executives and government officials said that even if all service stations here are short fuel by 3 to 8 percent, it will not necessarily mean lines at the gas pumps as during the Arab embargo in 1973.

"It's not a terribly serious problem," said Donald R. Healy, Shell's mid-Atlantic regional manager. "What it means is cutting out that one extra trip that people might make just for a loaf of bread."

Healy and others in the industry, however, said that if everyone panics and tries to fill up their gas tanks at once it will drain the supply system and create a shortage that would take from seven to 20 days for the supply system to fill again.

Healy made these estimates, which interviews with other industry sources tended to confirm:

Of the 800 Washington area stations whose suppliers have announced supply curtailments, only those who have experienced a growth in their business during the past year will be hurt.

They will be hurt because, under the federal allocation rules, they will be allowed to receive from their supplier in any given month only what they received diring the same month a year or more ago during a set "base period."

But if a station is selling less than it was a year earlier -- because business has dropped off or because the dealer has chosen to emphasize service over gas sales, for example -- its allocation will be higher than what it needs.

In Shell's case, 90 percent of its 165 stations here are selling more than they were during the "base peiod," so 90 percent of Shell's stations here will be hit by curtailed supplies.

Dealers at these stations will have to decide whether to close Sundays, cut their weekday hours or close during a weekday in order to string out their available supplies through the month -- thus not losing any more customers than necessary.

Healy and others estimated that as many as 400 stations here will choose Sunday closing on the last day of this month.

"If March turns out to be just the opposite of February, with excellent driving conditions on all weekends, it's quite possible that the last Sunday of March we could have 90 percent of our Shell stations closed," said Healy.

"April is a better example because there are five Sundays," said Healy. "On the 29th, assuming (good driving) conditions and everybody on (Curtailment), that last Sunday there literally could be 100 percent of all stations of all companies closed regardless of what DOE mandates."