Bhutan, a tiny Himalayan kingdom, is not known to have any steel-making capacity. But it became a supplier of steel to the United States this year, shipping 55 tons through September.

The Republic of Kiribati, formerly known as the Gilbert Islands, is another first-time supplier to the United States while apparently lacking any steel-making capacity, shipping 30 tons through September.

Its Pacific Ocean neighbor of New Caledonia, a French possession off the coast of Australia that specializes in raising cattle, coffee and vegetables, supplied 604 tons to the United States in the same period.

They are among 18 countries that have sold steel to the United States this year even though records show them lacking steelmaking facilities.

The American Iron and Steel Institute (AISI) called that trend "disturbing" even though shipments from the 18 countries amounted only to about 10,000 tons of total U.S. imports of 19 million tons. Industry officials suspect the surge of first-time suppliers reflects a deliberate attempt by foreign steelmakers to find loopholes in President Reagan's year-old program to limit imports to 18 1/2 percent of the U.S. market.

"Clearly the transactions involved in these cases need to be carefully checked by the Department of Commerce to ensure against violations of the president's import restrain program," the AISI said.

"The possibility is raised that imports through these non-regular channels may become a disruptive influence on the U.S. market," the steel association added in a statement yesterday.

Government statistics showed that imports from the 15 nations that negotiated restraint agreements with the United States dropped 14.4 percent in the first nine months of the year. But imports from other countries, mostly small suppliers, increased by 19.8 percent, the AISI noted in its analysis of the nine-month totals.

There were, moreover, 80 countries that supplied steel to the U.S. market so far this year, compared with 59 during the same period in 1984. Only six countries with no steel-making facilities listed in the latest editon of "Iron & Steel Works of the World" supplied steel to the United States last year, compared with the 18 in 1985.

Reagan administration trade officials are aware of the problem. One commented that steel is "squirting into the country like Jell-o" since the quota agreements.

U.S. steel makers acknowledge the possibility that some of these non-producing nations may have gotten on the list through a mistake by U.S. Customs or Commerce officials, who could have punched the wrong country code numbers into a computer.

Most likely, industry sources said, "the stuff is just being fraudulently invoiced" -- marked as coming from a country with no quota when it really originates in the mills of a regular supplier.

"What you have here is transshipment fraud, some of which may be very blatant," said one industry official.

U.S. officials have noted similar examples in textiles, although in many cases the garments actually are transshipped from one country to another to avoid quotas. Steel, though, is considered too heavy to move around that way, causing industry officials to believe only the invoices are changed.

Fred Lamesch, head of the American Institute for Imported Steel and president of TradeArbed, an importing company, discounted the AISI concerns and denied there was fraud involved.

"I think they are trying to make a mountain out of a molehill," he said. "The U.S. market is like a magnet. It attracts product from all over the world because it offers prices 20 percent to 30 percent higher than anywhere else in the world."

He added that the small amounts of tonnage shipped by non-producing nations "are meaningless" because it costs more to transship steel than the tonnage is worth. He suggested that some countries may have small facilities that convert one steel product to another -- imported wire rods to nails, or hot band to pipe, for instance.

The Bahamas, listed by the AISI as a nation without steel producing facilities, may be one of those cases. According to the CIA's "The World Factbook," one of the Bahamas' major industries is making steel pipe.

Some other countries, however, are situated next to major suppliers who agreed to limit their exports to the United States. For example, four of them -- Antigua, Barbados, Netherlands Antilles and Dominica -- are Caribbean islands off Venezuela, whose steel shipments were cut back. Two others, Namibia and Swaziland, have close economic links to South Africa, which also reduced its steel shipments.