The School of Advanced International Studies (SAIS) here and the Wharton School of the University of Pennsylvania have tied the knot, in the name of the MA, the MBA and three years of graduate school instead of four.

This union between SAIS--which is part of Johns Hopkins University in Baltimore, and Wharton apparently will represent the first time that two unrelated institutions have joined to offer a combined three-year Master of Arts in International Relations and Master of Business Administration degree program.

"I do think we'll see a lot of new applications--people who had to make a choice" before between business school and international relations, said Wharton's point man for the project, Vice Dean Everett T. Keech.

The combined program will offer a hybrid education, giving the business executives and public servants of tomorrow an understanding of complex international politics as they relate to world trade.

Next January, two or three students from each school will head off to study at the other for a year and a half. In the ensuing experimental years of the program, an exchange of no more than 10 students from each school is anticipated.

Even though the union was not announced publicly until today, it has generated a lot of interest.

"We've been getting calls, people have been writing since last spring, calls from California," said George L. Crowell, who has been brokering the deal with Wharton for SAIS, where he is associate dean for student affairs.

At the the heart of the joint venture is mutual advantage.

"There are definite benefits to this SAIS' program, but in terms of marketability it helps to augment it with something else" like an MBA, said Susan Rice, a second-year SAIS student just back from programs in Italy, Poland and Hungary.

While the SAIS program includes courses in financial analysis and other quantitative methods, "it seeks to relate academic learning to the expanding variety of private and public activities involved in relations among governments and national societies," its catalog says.

Critics say MBA programs typically lack production-line orientation, emphasizing management for short-term gains instead of long-term health, and gloss over realities of the working -- and political -- world.

"I continue to be amazed at the lack of grasp of international affairs in business," SAIS Dean George R. Packard said recently. While not shy about saying that "the MBA has fallen into disrepute," he noted that possessors of such degrees are still in high demand.

In offering the program, Wharton and SAIS are seeking to achieve a combination that will ultimately improve U.S. private industry's performance in the fast-expanding world of international business.

Isaiah Frank, chairman of the International Economics Department at SAIS, pointed to the ongoing international financial crises--most spectacularly in Mexico, which owes billions of dollars to foreign banks--noting that many large private banks have failed to take into account factors in the Third World that go beyond usual business school curriculums.

He said SAIS students are better equipped than most business school graduates to analyze political developments, currents in international institutions such as the World Bank, developments elsewhere in the world, a given country's stability and attractiveness to business.

"Our fastest-growing industries . . . rely very heavily on the international market," he said. As evidence, he noted that in 1962 U.S. exports were 5.7 percent of gross domestic product, which measures production within U.S. boundaries. In 1980, exports were 13.2 percent of GDP.

In turn, he said, the Wharton partnership "responds to SAIS students' demands for more exposure to the private sector." hen SAIS was founded by Paul Nitze, Christian A. Herter and others in 1943, it was conceived as a training ground for the foreign service and other jobs in government. But the balance has changed, and now 40.4 percent of SAIS' more than 3,000 alumni are in private business; 47 percent of the class of '81 went into business and 20 percent found work in government at the federal or local level or abroad.

Of Wharton's 1981 graduating class, 52 percent went into service industries such as investment banking and consulting, while just one percent headed for government service.

"I've got to give our students credit for going after the experience rather than salaries," said Maureen Golden, director career services at SAIS. She said some SAIS graduates do volunteer work on Capitol Hill "just to get their foot in the door," while others obtaining entry-level research jobs in private industry earn about $15,000 a year. An average salary for SAIS graduates is in the low- to mid-20s, she said. But after SAIS graduates become established in their careers, she added, they generally move into high-paying jobs.

Wharton's "fact sheet," meanwhile, touts "one of the best placement records of America's business schools."

"Last year," it says, "the Graduate Division was visited by as many recruiters (600) as there were graduates. Mean starting salary for 1982 MBA graduates was $30,200, up from $28,100 in 1980. Graduates were offered an average of 3.8 jobs each. Preliminary data show 1982 graduates are being offered between $32,000 and $36,000."

Golden says she is looking forward to "the halo effect" of the merger, in which SAIS students not directly involved in the Wharton program will be able to bask in the glow of Wharton's reputation and the advantges the association can bring to their careers.

Despite the apparent difference in callings, administrators at SAIS and Wharton say that the profiles of the two student bodies are remarkably similar.

Successful candidates for the joint program must be accepted separately by each school.

Wharton and SAIS share a cosmopolitan outlook, offering their students both formal and informal exchange programs with institutions around the world. And each is pioneering a program in the People's Republic of China.

In 1985, SAIS will open a center at the University of Nanjing that both Americans and Chinese will attend. Wharton has signed an agreement in principle to help Jiao Tong University in Shanghai, which Keech says is "sort of the MIT in China," to set up one or more business management schools.

While the SAIS faculty reportedly approved the proposed Wharton venture with little reservation, numerous sources said that Wharton had to overcome sensitivities from the faculty of its relatively small, more academically oriented international relations department, which also offers a combined MBA-international relations degree. rinceton's Woodrow Wilson School has joint-degree programs with the law schools at Columbia University and New York University. Students at the Fletcher School of Law and Diplomacy at Tufts Uniersity can cross-register at Harvard University. Separate from this, Fletcher has a joint program with Harvard Law School whose participants get their law and master's degrees in four years instead of five.

Asked for reaction to the new program, a spokesman for Peter Krogh, dean at Georgetown University's School of Foreign Service, said that "he had no comment except he's just delighted they're going ahead with it."

One source said, "I'd be willing to wager that the Fletcher School is shopping around now" for a similar program.

Fletcher Associate Dean Charles N. Shane said, "I think it's something we'd look into," possibly with either of the business schools at Harvard or MIT.