The flow of trade between the United States and South Korea has tipped sharply in favor of the Asian nation in the past year, under the weight of record imports of steel, textiles and electronics.

The persistent strength of the dollar has helped Korean traders, just as it has all foreign exporters who sell to the U.S. market. So has the exceptional strength of the U.S. economy in the past 18 months.

Beyond that, however, some analysts see the import surge as evidence that Korea is launching itself along the same path that Japan followed on its way to becoming an industrial superpower. Korea -- and Taiwan, Hong Kong and Singapore -- have been dubbed the "little Japans," and their exporting successes have raised new fears about the long-term competitiveness of U.S. manufacturers.

That thesis is challenged by other experts in and out of South Korea. What is clear is the escalation of the U.S. trade deficit with Korea.

Between 1980 and 1982, trade between the two nations was roughly equal in value, with the United States enjoying a surplus in 1980. But last year, imports into the United States from Korea shot up by 32 percent from the year before, according to the Commerce Department. Meanwhile, American shipments to Korea rose only 5 percent.

Korean imports here totaled $7.1 billion in 1983, exceeding U.S. exports to Korea by more than $1.2 billion. And in just the first eight months of this year, imports from Korea have reached $6.7 billion, raising the deficit to $2.5 billion and growing.

One measure of the impact of Korea's trade success is steel. Korea shipped 1.1 million tons to the United States in the first six months of this year, compared with 742,000 tons for the first half of 1983. The recent surge of foreign steel shipments -- that precipitated President Reagan's promise to seek voluntary import limits -- has been led by Korea and other developing industrialized countries. Together, they accounted for 40 percent of total steel imports through August of this year. Ten years ago, the same developing countries supplied only 8 percent of U.S imports.

To Bruce R. Scott, a professor at Harvard Business School, the meaning is obvious. "Our competitors are not the ones we think of," said Scott. It is no longer Europe, but Asia, particularly the newly industrialized developing countries, that represent the challenge.

This challenge is the centerpiece of a 2 1/2-year-long study by members of the Harvard University faculty, edited by Scott and George C. Lodge of the Harvard Business School and scheduled for publication next month.

What Japan and the "new Japans" have in common, say Scott and Lodge, is a high degree of specialization in their exports, coupled with a pattern of upward adjustment from simpler, labor-intensive products such as footwear and textiles, into industrial commodities and finally, high-technology electronic products.

"Obviously they are not as far up the scale as Japan," said Scott. (In 13 of the top 20 trade categories studied in the Harvard report, the market shares of the developing nations are below worldwide averages.) "But they show a decline in only one category, vehicle parts," Scott said.

"The pattern is almost more striking than Japan's; in 15 or 20 years they accomplished what the Japanese did in 25 or 30. It is possible that in another decade, a dramatic thrust toward higher technology exports and formidable competition from these newcomers will affect all the older industrial countries," the Harvard study said.

"These countries have succeeded not only in shifting their export mix from raw materials to manufacturers at unprecedented speed, but also in moving upscale technologically at the same time," they said.

The model is one of "managed" competition, in which business leaders and government bureaucrats work in concert to mobilize technology, capital and skilled labor to attack high-priority markets, just as Japan did in the steel and shipbuilding industries 20 years ago and is now doing in supercomputers and biotechnology. And at the same time, bureaucrats pressure businesses to move more rapidly out of declining industries.

Today, when money and technology are more mobile than ever, a second-ranked manufacturer can close the gap with the leader more rapidly than ever by channeling investment and skilled workers into a targeted industry, says Scott.

And among the Pacific Rim nations, targeting is customarily coupled with government policies that protect domestic industries until they have enough strength to jump into world markets.

Chalmers Johnson, professor of Asian studies at the University of California at Berkeley, speaking at a conference on industrial policy sponsored by the American Enterprise Institute, said:

"I do contend that the Japanese have put together the political and economic institutions of capitalism in ways that differ from the Anglo-American model. . . .

"The most obvious tradeoff is that in return for lesser levels of political participation than those prevailing in the United States, Japan has obtained a comparatively more effective and more efficient public economic policy."

There is nothing exotic about it. The Japanese method gives a fundamental emphasis to the economic competitiveness, a priority that pervades government and private business decision making. And it removes questions about industrial strategy, as far as possible, from the political arena -- exactly opposite to the practice in this country, where industrial policy sharply divided Republicans and Democrats.

But other academics challenge whether Japan's miracle can be copied. "It's overstated," said Tun-Jen Chen, a Brookings Institution fellow who recently visited Korea. "There is no comparison with Japan -- even comparing Korea and Taiwan now with Japan in the 1950s, there is still a gap."

"Their timing is bad," he said. Japan's miracle growth was achieved during the 1960s and 1970s, when barriers to international trade were being eased. Now, Korea, Taiwan and the other Pacific Rim nations must succeed in a world economy that is growing more slowly, creating rising pressures for trade protection.

Japan also benefited enormously from a carefully structured tax and banking system that channeled savings from consumers to industry through tax incentives and controls over interest rates. Korea's financial markets are not nearly that controlled, thanks to an "underground" economy involving businesses that aren't targeted for government-backed financing, said Chen.

Chen also questions whether Korea has the internal cohesion to imitate Japan's industrial growth. "I don't think Korea and Taiwan's planners and business executives are working as closely as Japan's did. Japan's industrial policy worked so well. . . . People tend to think there is a Korea, Inc. It's not the case."

In any case, there is no possibility that the United States might copy Japan's industrial strategy successfully, argues Johnson, because the Japanese success was based on the leadership of a powerful bureaucracy and a compliant legislature, working in close partnership with industrial leaders. Those conditions are not part of the American political culture.

What the United States should be doing, he told the AEI conference, is trying to resist protectionism, on the one hand, and on the other, closely examining its own economic, budget and trade policies to see how they help or harm the strength of U.S. traders.