The business allure of the Pacific Rim, which in recent years has enticed an increasing number of American companies, has also cast its spell over the insurance industry.

America's largest insurers, including Aetna Life & Casualty Co., Cigna Corp., American International Group, the Hartford Insurance Group and others, are selling life insurance, property-casualty insurance and other financial products in the region, which includes Japan and the so-called Four Tigers -- South Korea, Taiwan, Hong Kong and Singapore.

These countries have large populations with growing middle classes able to afford discretionary items like insurance, analysts note.

"We're very excited about the prospects in the Pacific Rim," said Bruce K. Howson, the president of Cigna Worldwide Inc. "We view growth prospects to be greater than in other areas."

Howson said that in 1987, Cigna's revenue in the Pacific Rim, where it employs about 1,800 people, was about $500 million.

Other companies also are bullish on the area. "Aetna's activity in the area is a function of ... high growth in these economies and their potential for the future," said James J. Mallozzi, Aetna's senior investments officer.

"It's part of the globalization of financial services," said Brant W. Free, the director of the Commerce Department's office of financial services. "You look around to where the money is." Free said that insurers have been slow in discovering prospects in the Pacific Rim, where the middle class is becoming increasingly concerned about savings and how to protect it.

"More and more people look to insurance as an investment to secure their future. That's a phenomenon of middle classes everywhere," he said. Insurers recently gained a beachhead in South Korea, the 10th-largest insurance market in the world, where life-insurance premium volume has been growing between 27 percent and 40 percent annually in the past five years, said Free.

After intense negotiations during the past two years in which the United States came very close to trade retaliation against South Korea -- the United States recently reached an agreement with the South Koreans allowing U.S. life insurers to form joint ventures with all except the 15 largest Korean companies.

"American companies over time should have a chance to gain a significant part of the Korean market," Free said. "We weren't just interested in nibbling around the edges." In 1985, South Korea had $5.5 billion in insurance premiums, of which $4.5 billion was in life insurance.

In Taiwan, Free said the United States used a "carrot instead of a stick" to increase the U.S insurance presence. Taiwan agreed in the summer of 1986 to permit five new U.S insurers expanded entry; the government also agreed to allow two new life and two new property-casualty companies to enter yearly. Taiwan had insurance premiums of $2.3 billion in 1986.

The insurers' drive to enter the Four Tigers also is being bolstered by the Reagan administration's recent decision to harden its trade policies toward these countries, in part to get them to open their markets further to foreign investment.

However, Free said Japan remains a tough market for U.S. insurers to crack because of restrictions it places on the introduction of new insurance products and generally cumbersome rules, which have deterred many U.S. companies. "Japan is geared to stability. It would require a major effort by U.S. insurers to get in there," he said.

Some companies acknowledge that caution is warranted, largely because the payoff is not immediate and requires considerable effort. They also say that in some countries, like Japan and South Korea, there are sizable obstacles, both cultural and political, to success.

"All of this is going to take time to develop," said Gordon J. Cloney, the president of the International Insurance Council, a trade policy lobby for the industry.

A snapshot of the variety of insurance operations in the region is offered by a look at what some of the leading companies are doing:

The American International Group, which traces its roots to a company founded in Shanghai in 1919, is an old hand in the region. Japan is the leading foreign market for AIG. The insurer received about $1 billion in gross premiums in Japan in 1987, primarily in property-casualty. AIG operated in South Korea on a restricted basis for about 10 years until mid-1986, when it was allowed to participate in the Korean Fire Insurance Association, which writes most of that country's property business. In 1987 AIG gained permission to write life insurance policies.

Cigna Corp. said Japan is its third-largest market after the United States and the United Kingdom. Howson said that in 1987 the insurer had revenue in Japan of about $300 million, compared with about $1.3 billion in Europe.

In South Korea, Cigna sells life and property-casualty insurance and has been doing a limited business there for about 15 years. However, Cigna has won broader authority in both areas and will be increasing its operations. Howson said Cigna had about $8 million in property-casualty revenue in South Korea in 1987.

Cigna's Hong Kong operation, where it has been since 1948, also handles its businesses in Taiwan and Macao. Last year, the three countries had about $20 million in property-casualty revenue.

Cigna also has insurance operations in New Zealand, the Philippines, Singapore, Malaysia and Thailand, and in Australia it had about $75 million in revenue in its property-casualty business for 1987.

Aetna is optimistic about the Pacific Rim and is focusing its efforts on insurance and financial services. On the insurance side, Aetna has a regional base in Hong Kong where it has three ventures, which had about $18 million in new sales in 1987.

One company, a joint venture with the Bank of East Asia, is focusing primarily on selling insurance to middle-class families. Another joint venture in which Aetna has a 50 percent stake, caters mostly to the American community in the region.

Mallozzi said Hong Kong serves as a regional center for Aetna's investment programs with its company called Federated International (FE Ltd.), which manages about $400 million for pension funds, mutual funds and private clients. In addition, Aetna will be opening an office in Tokyo this year that will serve as an investment adviser to Japanese clients like the Bank of Tokyo on investments it makes outside of Japan. Travelers Corp. has set up partnerships with local companies in Japan, South Korea, Hong Kong, Australia, Malaysia, Singapore and Indonesia that allow the local insurers to write the business and service the clients for Travelers. In the United States, Travelers performs a similar function for them.

Travelers' business is aimed at the subsidiaries of U.S. multinationals. The Hartford Insurance Group d1768169569an international volume of $1 billion, said Lawrence S. Doyle, president of Hartford Fire International Ltd. He said the firm is seeking insurance business with small and medium-size U.S.-based companies in the region.