Some 150 nations will gather in Mexico City in August to consider the crucial issue of global population growth and how to control it. What will the United States position be?
That is a delicate question here as President Reagan appears to want to change longstanding American policy. Some elements in the White House would like to end all US family-planning assistance to governments and private organizations that support or advocate abortion services.
A White House draft position paper calling for such a change of policy has stirred a storm of controversy in and outside the administration. Right-to-life groups are pitted against strong population-control advocates.
Family-planning groups, population control organizations, lawmakers, and officials of the State Department and the Agency for International Development (AID) are voicing concern about the draft paper and are lobbying to see it reversed.
Administration officials are reluctant to comment. But one White House source says the matter is under review and that, while there may be an internal battle over the issue, the present bipartisan US policy is certain to continue.
The United States has long banned aid to developing countries for abortion services. Its family-planning assistance stresses other birth-control methods. And such aid has not been contingent on a country's acceptance of any specific population policy.
Many see election-year pressures behind the White House proposal, prepared by the Office of Policy Development.
''Right-wing forces have spread their tentacles into various parts of the government and are making a pitch at election time,'' says Marshall Green, a director of the Population Crisis Committee. ''The proposal is a disaster and will be deeply offensive to our friends abroad - Egypt, India, and others - that are moving ahead on population programs and have counted on aid from outside groups, including the US.''
In a letter to the White House, Werner Fornos, president of the Population Institute, said, ''The draft was quite obviously influenced by a vocal minority that has been clamoring for the dismantling US population assistance.''
Three senators - Charles H. Percy (R) of Illinois, Alan Cranston (D) of California, and Charles McC. Mathias (R) of Maryland - also have written the President expressing concern over the proposed change of policy.
And, according to informed sources, Senator Percy raised the issue when he met with Mr. Reagan last week to talk about a US-Soviet summit meeting.
AID, too, is trying to alter the White House-proposed US position at the International Conference on Population opening Aug. 6. In a memorandum to the White House circulating here, AID states that ''by focusing on what an organization advocates, as contrasted with what it does, the (White House) statement will be extremely, and in our view unnecessarily, controversial.''
AID, according to the memorandum, favors conference approval of a recommendation urging aid ''to help women avoid abortions.''
Such a recommendation, in AID's view, ''puts a UN intergovernmental population conference on record for the first time as not favoring abortion, a position fully consistent with US policy. Securing an explicit conference condemnation of abortion, on the other hand, is unlikely because of the legally approved status of abortion in most countries.''
Right-to-life groups are in turn lobbying vigorously in favor of the White House proposal.
''We are totally supportive of and have pressured the Reagan administration to hold firm,'' says Judie Brown, president of the American Life Lobby. ''The US government through taxpayer funds should not involve itself in the sexual habits of couples of third-world nations.''
The May 30 White House draft position paper states that the US does ''not consider abortion an acceptable element of family-planning programs'' and ''will no longer contribute directly or indirectly to family-planning programs funded by governments or private organizations that advocate abortion as an instrument of population control.''
If this, indeed, becomes White House policy, it is estimated that developing countries would stand to lose perhaps half of the $240 million spent annually on population assistance. It is not only the stand on abortion that distresses many population experts, but the general tone of criticism of other goverments.
The White House draft paper says that population growth has changed from an ''asset'' to a ''peril'' because of ''government control of economies'' and an outbreak in the advanced countries of an ''antiintellectualism, which attacked science, technology, and the very concept of material progress.''
Population control will not solve unemployment, states the position paper, which will persist ''as long as oppressive economic policies penalize those who work, save, and invest.''
Such language is ''insulting,'' comments Mr. Green, a former US ambassador and a consultant to the State Department on population matters. ''It's the kind of thing where we're trying to pass moral judgment on other countries.''
The leaders of Egypt, Pakistan, Indonesia, India, and other countries, Mr. Green says, are valiantly trying to bring population growth under control and have gone out on a limb in support of family-planning programs. ''They may find abortion abhorent,'' he says, ''but if they don't provide abortion services, such services will be provided by quacks, with tragic consequences.''
Population experts see family planning not merely as a social necessity but as a strategic and political imperative.
With population growing and pressures on the environment and on resources increasing, the argument goes, conditions are created for massive unemployment, food shortages, internal political turmoil, and tensions between the have and have-not countries. Global stability could be threatened.
Robert McNamara, former president of the World Bank, warns against complacency based on the UN's report that the world's population growth has declined over the past decade. This drop, he writes in the new issue of Foreign Affairs, has taken place almost entirely in the advanced nations not in the developing world.
Unless the rate of increase can be brought under control in the third-world countries like India and Nigeria, he says, it will lead to even more abortion and infanticide, massive unemployment, poverty, and authoritarianism. He urges even more attention to and assistance for population control programs.
President Reagan appears to have a political hot potato on his hands in an election year. Observers here wonder to what extent he was personally involved in the White House draft position paper.
While Reagan is a strong opponent of abortion, he has been a supporter of family planning since his gubernatorial days. And only last year his secretary of state told a gathering that US assistance for voluntary family-plannng programs abroad has been ''an effective effort'' and that ''we have a deep interest in continuing it.''