Millions of Third World women want to limit the number or control the timing of their pregnancies, but most lack access to family planning, the Worldwatch Institute said yesterday.

Although world population growth has slowed since the 1970s from 2 percent to less than 1.7 percent per year, "annual additions to world population increased from 74 million in 1970 to 86 million in 1987," said Jodi Jacobson, author of a new study.

The study, "Planning the Global Family," said that if the needs of even half the women lacking access to family planning had been met, "annual additions to human population would now be falling instead of rising."

The Worldwatch study cited surveys showing that half the 463 million married women of reproductive age in developing countries outside China want no more children. Millions of others, it said, would like to delay their next pregnancy.

"Yet, while the number of women in their childbearing years is increasing rapidly, few countries have put family planning at the top of their agendas," said Worldwatch, a non-profit research organization that focuses on global and environmental issues.

Jacobson also said that the United States has "abdicated" its role as a leading supporter of reproductive rights worldwide.

Total U.S. international population assistance fell 20 percent between 1985 and 1987, the study said, from $288 million to $230 million.

The study also said that only four developing countries have achieved replacement level fertility, or two children per couple: Cuba, Singapore, South Korea and Taiwan. It said that while impressive reductions have been achieved in Brazil, China, India, Indonesia and Mexico, fertility rates remain moderately high -- 3.5 children per woman -- in all but China.