More than half of the world's new telephone subscribers in 1996 were mobile cellular, and for the first time surpassed new fixed-line subscribers, an industry report said.

In affluent nations, mobile cellular accounted for nearly 75 percent of all new phone subscribers, said the report by the International Telecommunications Union.The study said the number of new mobile cellular subscribers in 1996 reached 54 million, up sharply compared with 35 million new cellular mobile customers registered in 1995, and 21 million in 1994.

In comparison, the total number of new fixed-line subscribers increased by 50 million in 1996, also up compared with the figure of 46 million notched in 1995.

The ITU study, titled, ''World Telecommunication Development Report,'' also predicted that the size of the global network of main lines will reach nearly 1 billion lines by the year 2000, up from the figure of 800 million at the end of 1997.

ITU communications economists pointed out that a combination of rapid technological developments and the trend of privatizations and liberalization are changing the structure of the industry.

The emergence of the fax, mobile cellular, and the Internet are having a profound effect, it said. The privatization of telecommunications operators is also ushering in long overdue competition and putting downward pressure on carriers to slash tariff rates.

In 1996, there were 142.1 million mobile cellular subscribers worldwide, or 16.1 percent of the total phone subscribers. The United States was the leading market with 44 million subscribers (in 1990 there were only 5.2 million). The next most important market was Japan, with 26.9 million. Six years earlier, Japan had only 868,000 subscribers.

The report notes that Argentina, after privatization, almost doubled its teledensity (phone lines per 100 inhabitants) from 9.5 to 17.7, while Chile and Venezuela lifted their teledensity to more than 10.

But the report highlights a big telecommunications gap still exists between rich and poor nations.

It points out that in 1997, 62 percent of all main lines installed were in just 23 rich industrialized countries, which accounted for only 15 percent of the world's population.

Moreover, 84 percent of mobile cellular subscribers, 91 percent of fax machines, and 97 percent of all internet computers are located in the wealthy nations.

It adds that 90 percent of households in rich countries have a telephone, compared with 16 percent for the rest of the world. ''Over 950 million households in the world, 65 percent of the total, do not have a telephone,'' the report said.

The ITU estimates that, overall, 500 million households, or 34 percent of the world's total households, have a telephone service. But the study noted, ''This could be increased to almost 800 million (55 percent) if service were uniformly available and sensibly priced.''