World leaders have made an important promise to the children of the world. Only time and the actions and priorities of the individual nations will tell whether that commitment will be honored.

During the September World Summit for Children, 150 of the world's leaders, including 71 presidents and prime ministers, vowed to work to better the lives of children worldwide and to end mass child deaths and malnutrition by the year 2000. They also promised to provide basic protection of the lives and development of children everywhere.We've only got nine years to make it happen.

If the goals are to be met, it will take hard work and careful planning around the globe. The cost of implementing the goals is estimated at about $20 billion a year, a figure that may seem overwhelming. Actually, though, it's roughly equal to the amount spent worldwide on the military every 10 days.

A report issued this week, "The State of the World's Children 1991," examines the goals both industrialized and developing countries have set to achieve secure futures for the world's young. The report was issued by the United Nations Children's Fund.

Leaders attending the summit, held at the United Nations in New York, came up with 20 recommendations. Some of them are so basic it's hard to believe it took a meeting of world leaders to address them.

The list of goals includes:

- Cutting the childhood death rate by one-third. More than a quarter of a million children die each week in the developing nations.

- Basic education for all children and primary school for at least 80 percent. Only half of the children in the developing countries complete primary school; boys had twice as much opportunity as girls for this basic education.

- Reducing malnutrition by half. The annual cost is estimated at $10 a child.

- Cutting maternal deaths by half.

Targets have been set for eradicating disease. Measles, for example, which kills 1.5 million people a year and is a major cause of malnutrition, should be reduced by 95 percent, according to the summit recommendations. Other targeted illnesses include polio and neonatal tetanus (preventable through good hygiene and immunization of women).

Perhaps the most tragic problems among the poor, because of their easily preventible nature, is the rampant blindness caused by lack of vitamin A and the mental retardation caused by insufficient iodine. The cost of the vitamin A and iodine is about a dime per child per year.

The summit recommended that industrialized countries like the United States use the goals as a basis for determining foreign aid. Aid should not be given, it said, to countries that do nothing to end the exploitation, abuse and illness of the youngest citizens.

An excessively idealistic suggestion? Maybe. But one way of measuring the worth of any society is according to how much it protects its weakest members. Few are less able to protect themselves than are children. And too many countries are flunking this simple test.