Caught on the horns of a dilemma, the authorities reluctantly are allowing sales clerks from other countries to work behind the counters in Singapore department stores.

On the one hand, officials don't want their booming economy to suffer from a lack of labor. But they are equally determined not to let the country depend indefinitely on low-skilled foreign workers. No quick solution is in sight.In announcing the budget last month, Finance Minister Richard Hu noted that a controlled revolving pool of foreign workers on short-term work permits would be allowed to continue beyond 1992.

The demand for foreign workers has been increasing rapidly. More than half of the 48,000 jobs created in the manufacturing sector last year were filled by foreign workers. In the last three months, manufacturing companies have been recruiting about 2,500 foreign workers each month, Mr. Hu said.

Bolstered by strong overseas demand and foreign investment, the economy has bounced back from a recession three years ago. But a limited labor pool in this city-state of 2.6 million people is now regarded as a threat to continued growth.

Help-wanted ads cram the newspapers. Signs offering walk-in interviews leading to instant vacancies are posted outside dozens of factories. With workers able to pick and choose, job-hopping is common, especially in the electronics industry.

Economic expansion generated a net increase of 66,000 new jobs last year, according to Ministry of Trade and Industry figures. The economy grew by 8.8 percent, compared to 1.8 percent in 1986. Unemployment was 2.8 percent at the end of 1987, against 4.6 percent at the beginning of 1986.

The boom is exemplified by Seagate Technology, the largest single private employer. The U.S. disk-drive manufacturer started operations here six years ago with 50 workers and now employs 13,000.

The United States decided in January that Singapore, known along with Hong Kong, Taiwan and South Korea as the fast-growing Four Dragons of Asia, is no longer a developing country in need of special trade preferences. Duty-free access to the U.S. market for the exports of all four is to be ended.

Established department stores complained earlier this year of a shortage of about 2,000 sales clerks. Newly opened stores were able to lure away such personnel from older retailers by offering high starting salaries. Older merchants could not match the money because of a wage freeze imposed during the recession. They appealed for government help.

Labor Minister Lee Yock Suan told Parliament recently that labor-starved storekeepers could now hire foreigners providing they had the equivalent of a high school education.

One chain of eight stores advertised in neighboring Malaysia for counter staff, so far with indifferent results. The Malaysian economy also is thriving, absorbing much of the labor Singapore stores and factories seek, and at least one retailer suggests that the educational qualification is too stringent.

Until the stores got help, aliens with work permits could be hired only in construction, manufacturing, hotels and as domestic servants. These jobs often are spurned by increasingly affluent Singaporeans, who enjoy the highest standard of living in Asia after the Japanese.