IF Pakistan continues to grow at the current rate, its 114 million population could easily double in two more decades. That prospect has spurred Islamabad to make a strong new commitment to family planning.At a briefing recently at the United Nations, Syeda Abida Hussain, adviser on population to the president of Pakistan, said the government's July decision to broaden and give new energy to a long-established family-planning policy stems from a sense of responsibility that is both global and national. "We see it as part of a new pledge to the world community.... Unless we contain our growth rate," she says, "we will no longer be in a position to improve education, health, and other... social development." Also at the briefing was another Pakistani: Nafis Sadik, executive director of the United Nations Population Fund (UNFPA). She is just back from Mongolia and Namibia, where she helped announce and explain similar governmental commitments to family-planning programs. Such high-level public support for family planning is coming along more rapidly than in years past and is viewed as increasingly important. "In almost every case where there's been a success story in bringing down fertility rates, there's been a strong commitment from the nation's leadership," says Harold Burdett, a spokesman for the Washington-based Population Institute. "Lack of political will in the developing world is no longer the big stumbling block it once was." During an interview in her office a few blocks from the UN, Dr. Sadik explained that top-level support for family planning helps not only to build public acceptance but also encourages lower-level bureaucrats to get involved in making such programs truly national. "Everybody must be invited to be an active participant and supporter," she says. Steady efforts through this and other strategies over the last three decades to curb skyrocketing world population growth are beginning to pay off. The rate of increase in annual births is slowing. More than half of all couples in developing countries - compared with 10 percent in the 1960s - now use contraceptives. More women say they want smaller families. Family size has dropped from a global average of six children in the early 1960s to 3.8 children in 1991. More nations now see a direct link between rapid population growth and environmental devastation and poverty. Much of the spread of family-planning services in recent years has come through adding them to established maternal and child-health care programs. "While that infrastructure may not be great, it's the easiest route and in almost every country provides the broadest network of service points," says Everold Hosein, director of program support for the Western Hemisphere office of the International Planned Parenthood Federation. But Dr. Sharon Camp, vice president of the Population Crisis Committee, cautions that one problem with using such channels is that they tend to reach women only after they have their first child. Delaying that first birth, she notes, can greatly extend the span between generations. No one in the field minimizes the challenges ahead. World population - now 5.4 billion - has more than doubled just in this century and is expected to hit 6.2 billion by 2000. By UN forecasts, the number will double again, or perhaps triple, before stabilizing during the next century. "We're making progress, but it's slow and I think we could do a lot more," Sadik says. She hopes that specific goals and an even broader consensus on the need for action can be reached at a 1994 UN conference on population. Population experts have learned much in recent years about strategies that work. More attention to women's needs, including education, health, and income-generating activities, is now seen as key. "Economic independence is very important," Sadik says. "Women then seem to do more of the decision-making.... There is a very important connection between control over life circumstances and number of children." UN data indicate that women with more education tend to have smaller families. Since many girls are pulled out of school to work in the home or marry, UN agencies are searching for ways to keep them in school once they are enrolled. "When they're not educated, women do what their family or their society tells them to do," says Sadik. Most family planning programs now also focus much more attention on male responsibility. AIDS has spurred wider use of condoms. Yet condoms and vasectomies account for only about 15 percent of contraceptives use in developing nations. Since many couples in developing countries communicate little, if at all, with one another about family planning, approaching men and women together is considered important. Yet population experts say that men as a group also need to be approached. International Planned Parenthood's Dr. Hosein says important inroads are being made in Ghana, for instance, by involving men through soccer clubs and other sports associations. Another effective strategy used in Peru, Guatemala, and Brazil, he says, is the use of clinics for services and counseling offered specifically to men. Concern about AIDS, the growing migration from rural areas to cities in many developing nations, the global decline in infant mortality, and improvement in life expectancy are all seen as positive factors to some degree in encouraging use of contraceptives and slowing birth rates. Yet cultural barriers in many regions remain strong. Longtime family-planning efforts in India, Pakistan, and Bangladesh, for instance, have made little progress so far. "Somehow we don't seem to have found the button we can pu sh to make the change - it's definitely a cultural thing," Sadik says. Both to increase research into such issues and broaden the reach of services, Sadik urges that spending on family planning by various world agencies be doubled to $9 billion a year. A large share of family-planning funds now come from developing countries themselves. "They can't do it alone," insists Mr. Burdett of the Population Institute. "The industrialized world has to understand how much the lack of more help is holding these countries and the whole global economy back."