A decade ago, if a business executive walked into a Washington bank with an order to ship $5 million worth of widgets to a foreign customer and asked for financing, the answer likely would have been the same, no mater which bank was picked.

"Go to New York," the Washington bankers would have replied. "We're not in the international business."

Today, the four biggest banks in the District of Columbia all probably would take a shot at that kind of an export financing deal.

A couple of them might even be interested in financing an overseas widget plant, if the project weren't too ambitious.

One local banker, J. William Middendorf, chairman of Financial General Bankshares reffered to Washington at "the ne international banking capital" in a talk last week on doing internation business in Washington.

A conference on that topic, put on by the D.C. Bar Association and the Metropolitan Board of Trade, drew 200 people - surprising even its organizers with the interest shown in international business, particularly finance.

Although most other bankers regard Middendorf's proclamation as premature, the growing importance of international business to the city's banks is easy to trace.

Financial General is developing its international department under senior vice president Richard Barrett at Union First National.

Riggs National Bank has built its international department up to 40 people under senior vice president James D. M. McComas. Riggs President Danial J. Callahan III was in international banking before he cames to Washington.

Next door at American Security Bank, international business that was once funneled through a branch in the Bahamas is now handled by a full-fledged subsidiary that opened its doors last week. Riggs senior vice presidents Gene Bennett and William Ryland recently switched jobs, with Bennett taking over corporate banking and Ryland moving into the international office.

National Bank of Washington, though smaller than Riggs or American Security, has sought aggressively to participate in international financing syndicates, usually with a New York institution as lead bank.

Attracted by the potential prof-its of international banking, NBW has opened the Nassau office that is needed to handle Eurodollar business and is looking for more of it. "We may not be ablt to run," with the New York Banks, "but we certainly can walk," NBW Chairman Donald Notman said last week when he was on the same program with Middendorf.

Running with the New York banks is impossible because of the size of Washington's banks. Even the biggest of the regional banks are small by money center standards, with lending limits too low to handle what is known as "project financing."

Financing multi-million projects - like an oil refinery or a farm equipment plant - requires on not only capital, but also expertise, both in the business and the country involved. With its 40-person international staff, Riggs is nearing the critical mass needed to be a major participant in project financing.

American Security probably won't go that route but instead will act as a syndicate member and emphasize the foreign trading business. The start-up costs are lower and the risks less in financing exports by the many middle sized companies that can sell technology - the country's last natural resource.

Washington's greatest resource, as a banking community, is the federal government. Bankers here readily admit that access to and familiarity with government agencies can be as important as cold cash in building their international business.

"You can get more information here with a few phone calls than you can by spending three weeks in the field," says Robert Wieczorowski, an investment counselor andformer U.S. executive director for the World Bank.

But while Washington bankers have ready access to federal agencies and the resources of the federal government, the World Bank and related agencies they lack access to this country's central banking system.

A Federal Reserve Bank branch for Washington goes at the top of every banker's list of what the city needs to become an international financial capital.

Other priorities are suggested by John Clark, senior vice president of Porter International Co., a Washington firm that, like European merchant banks, brokers financing for businesses.

"If a major foreign bank were to buy into an Washington bank," Clark suggests, "that would give an international flavor and make a substantial contribution" to Washington's influence. (Clark says he's talking about a European bank that would bring international banking skills with it, not passive investors like the Arabs seeking control of Financial General.)

Clark also suggests that Washington's financial institutions "find a way to pool their resources" so they can together take the lead in project leading, a job that's too big for any individual bank here.

Finally, adds Clark, the Washington business community has to get involved with the international businessmen who come to the city daily to deal with the World Bank, the State Department or their own embassies.

In the capital of capitalism, visiting businessmen rarely have a chance to meet anyone who isn't on the government payroll. Business should roll out the red carpet, he says.