Since Sept. 30, containers the size of truck vans, filled with $100,000 in leather goods, plastics and other merchandise destined for the Design Store in Washington have been stranded on the docks of Baltimore harbor by a longshoreman's strike.

The items were bought last February, said Judy Newman, merchandise manager, "with an eye on having them in our stores for Christmas."

The Design Store, which sells imports goods from glassware to furniture and delicate Christmas ornaments, is one of a wide array of businesses suffering from dwindling inventories, increasing costs and inconvenience from the selective strike against the containers: those vast, sleek boxes that hold thousands of pounds of cargo and are unloaded off ships by giant cranes and placed on trucks to be hauled away.

The International Longshoremen's Association claims that the highly mechanized containers ships are responsible for a substantial reduction in jobs and work opportunities.

About one-sixth of the port's entire business has halted. Most of the 4,000 stevedores who normally load and unload the container ships have been out of work. So have numerous truckers - about 2,000 - who drive the cargo in and out of the port.

In ports from Maine to Texas, more han $4 billion worth of freight is tied up, according industry accounts. "If I don't get some tunafish in here within two weeks, I'll be hurting," said Rose Drylie, director of purchasing for Smelkinson Bros. Corp., which supplies canned vegetables, fish and juice to restaurants, hospitals and other institutional kitchens.

Household goods, such as the belongings of foreign embassy employees leaving Washington, are also stacked up in containers in warehouses.

Consequently, said Grant Cohen of Lion Transfer and Storage, seven men have been laid off. Cohen has also had to hire extra security guards for the, containers. "All my customers have had to put off their moves until the stike ends," said Cohen. "It hurts.Our warehouse is loaded with freight that we can't charge for because it's not our clients' fault."

Some businesses are using new, costly and circuitous routes to avoid the stike. Chrysler Exports for example, is moving its auto parts to Canadian ports for shipment to South America.

It costs two-thirds more to ship automobile parts this way.

The Hickory Farms store in Springfield, Va., has allowed its imported French cheese stock to dwindle "because we won't pay the price of air freight," said manager Gary Pazmay.

But at the Georgetown Coffee House, gourmet items and copper cookware are being flown into the United States. "The heck with them," Bob Wroe, business executive, said of the longshoremen. "This is easier, and I'd rather do business this way anyhow."

The U.S. Postal Service has embargoed surface mail to Europe, the Soviet Union, Greenland, Iceland, Africa, South and Cemtral America, the Caribbean Islands and the Middle East.

Tensions are mounting at the port. In Baltimore, for example, one longstoremen reportedly was ousted from a union local which he tried to buck management's fixed negotiating position.

In the U.S. Lines office in Dundalk, "We're catching up on our paper work, but by next week, we're not sure what we'll have to do," said Mike Gallagher. "People are starting to glare at one another."

The longshremen, who claim the mechanized container ships will eventually put them out of work, are seeking in Baltimore to secure a guaranted income for 2,080 hours of works. The current minimun wage for the longshoremen is $8 an hour.

"In my opinion, it's a do-or-die situation," said John Krysiak, an official of Longshoremen Local 333.

Among rank-and-file longshoremen, the strike has drawn varied reactions that illustrate the tensions with their own system. Some criticize union "politics" that led to a selective, rather than full-fledged, strike.

Others argue that the union leadership, when says it is attempting to find longshoremen at least one or two days of work each week, is showing preference to senior members when job opportunities open.

For example, young members regularly appear as early as 5 a.m. at a hiring hall, while others, like Paul Lengrand, 39, a longshoreman for 15 years, said that during the stike he is "making more money than I ever did in my life" because of the stevedoring opportunities sent his way.

"A lot of guys believe the strike is really crazy," said Donal Robinson, 27, of Baltimore. Since the strike began he has worked up to 30 hours some weeks and as little as 4 during others, or barely enough "to keep the landlord away from the door ."