President Zia is the most recent of a score of world leaders to visit the White House this year. Perhaps more than any other of these visitors, he brings with him a peculiarly complex bundle of security-related issues requiring Washington's attention and, as appropriate, assistance.
The most immediate and obvious security issue derives from the Soviet invasion of Afghanistan, Pakistan's neighbor, the flight of nearly 3 million Afghan refugees now encamped in Pakistan, and Soviet pressures on Pakistan to accept the legitimacy of the puppet regime in Kabul. A longer-range security problem for Pakistan has involved its relations with India and the status of Kashmir.
But the longest-range security-related problem confronting Pakistan is how to provide for, and meet the expectations of, a population of over 90 million people, growing at the astounding annual rate of 2.8 percent, as high as any in South or East Asia, which portends a possible doubling of Pakistan's population within 25 years.
President Zia is wisely seeking to grapple with all these problems simultaneously - and this necessarily involves better ties with the United States (short of relinquishing Pakistan's nonaligned status), better means for working out differences with India, and sustained efforts to carry out Pakistan's new comprehensive Population Welfare Program.
The fundamental importance of achieving population stabilization has been recognized by other outstanding leaders of the developing world who happen to have visited the White House during the past year, including President Suharto of Indonesia, President Mubarak of Egypt, President Marcos of the Philippines, President Lopez Portillo of Mexico, and Prime Minister Gandhi of India.
President Suharto, who has achieved considerable success in bringing down population growth through popular village-based programs, put the case for population stabilization most emphatically when he recently stated: ''It is not an exaggeration to say that the successful implementation of family planning programs will be key to the survival of the world of the future.''
There seems to be heightened awareness among leaders, especially in Asia, of how rapid population growth adversely affects a nation's stability, governance, and economy. It is becoming notably apparent that soaring levels of unemployment and overcrowded slums are almost certain to breed rising levels of mass frustration and alienation exploitable by forces of extremism.
Also evident is a sense of growing uneasiness in the donor community over how excessive population growth in recipient countries undercuts the benefits of investment including outside assistance. This is recognized in many developing countries, including Pakistan, whose new Population Welfare Program acknowledges: ''Population in-creases have wiped out the benefits that should have been forthcoming from sustained investments over long periods of time.''
Pakistan and its friends therefore have much at stake in the ability of Pakistan to carry out, at long last, the kind of comprehensive community-based population program it now seems prepared to launch.
But it faces enormous obstacles in doing so: traditionalism, illiteracy (especially among women), the weakness of village or community organizations, bureaucratic inertia, competitive politics and the distractions of immediate issues.
There are no simplistic solutions to problems of this magnitude and complexity; and those key US AID officials who in the 1970s advocated solutions primarily based on ''contraceptive inundation'' didn't help things much. Family planning and medical back-up are essential, but far more is involved.
What is basically involved is changing the attitudes of parents in predominantly rural Pakistan, who have various valid personal reasons for wanting large families, even though it is becoming painfully apparent that having, in the aggregate, such large families is contrary to the interests of their children, their communities and their nation.
This is no easy undertaking. It calls for sustained, humane efforts under dedicated leaders charged with a sense of urgency in addressing a long-term problem.