HOUSTON (AP) _ The United States and its trading partners agreed today to work toward a plan within the next two years to save the world's forests from destruction, but papered over their sharp differences on global warming in the interest of summit unity.

President Bush succeeded in keeping out of the final communique of the seven-nation economic summit any mention of European demands for target ceilings on emission of polluting gases blamed for a gradual increase in the Earth's temperature.

The summit leaders declared that ''we as industrialized countries have an obligation to be leaders in meeting these challenges,'' including climatic changes, ozone depletion, deforestation, marine pollution and loss of biological diversity.

Environmental groups denounced the communique as a do-nothing statement.

''Despite their green rhetoric, the ... leaders leave Houston in the red on the environment,'' said a coalition of prominent environmental groups.

''The summit is a failure on the environment because they did nothing on global warming,'' said Dan Becker of the Sierra Club.

The summit's agreement to devise a forestry action plan could help the eventual easing of global warming because trees absorb carbon dioxide, a major culprit among so-called greenhouse gases.

Scientist say 20 percent of global warming results from deforestation.

The United States agreed to join in working on ''appropriate implementing protocols'' as quickly as possible to stem the warming of Earth's temperature.

U.S. officials said the protocols should consider all sources of synthetic gases and such mitigating measures as tree plantings.

President Bush originally had said that these protocols should await an international agreement on global warming in 1992.

Meanwhile, at Bush's urging, the summit leaders agreed to begin immediate negotiations on curbing worldwide deforestation. The accord could include measures to prevent deforestation, replant industrialized areas, train Third World countries in forestry protection and discussions on control of acid rain and other issues, U.S. officials said.

The leaders said the forestry agreement should be ready for signing by 1992.

''The destruction of forests has reached alarming proportions,'' the communique said.

The summiteers also signed off on a deal struck Tuesday to implement a plan within one year to save Brazil's tropical rain forests, the officials said.

Summit negotiators also debated a U.S. proposal to strengthen the tropical rain forest rescue plan administered by the World Bank and various United Nations groups. Environmentalists have criticized the program a ineffectual.

During talks by the summit partners, representing the United States, Britain, France, West Germany, Italy, Canada and Japan, environmental issues were overshadowed by trade, farm subsidies and other matters, but there was general discussion of the so-called greenhouse effect produced by air pollutants.

West German Finance Minister Theo Waigel said the agreement included an urgent pilot project that would lead to a reversal of the current destruction of rain forests. Officials said the World Bank should oversee the project, but no cost estimates or other details were disclosed.

The decision to postpone action on global warming and hold a study conference conforms with Bush's contention that more research is needed before taking such dramatic steps to curb global warming.

When the Economic Summit countries met a year ago in Paris, they agreed to ''common efforts to limit emissions of carbon dioxide and other greenhouse gases which threaten to induce climate change.'' Environmental groups have accused the United States of failing to live up to that commitment.

The European Economic Community on Tuesday challenged the Bush administration to prove its contention that taking dramatic steps to halt the warming trend will stall economic growth.

Jan Laurens Brinkhorst, director of environmental matters for the European Economic Community, said the facts do not bear out the theory that curbing carbon dioxide emissions will slow economic growth.

Carbon dioxide is produced by the combustion of all fossil fuels.

Brinkhorst said the world economy grew by 25 percent between 1973 and 1986 while energy consumption remained flat.

Economists agree, he said, that energy use could be reduced 15 percent to 20 percent in the course of a decade without major economic disruption.

''I would hope to see, in a serious way, the Europeans and Americans compare notes and actually see what is true, (whether) you would have this tremendous difficulty in your economic performance if you would do something more'' about carbon dioxide emissions, Brinkhorst said.

Carbon dioxide has been estimated to account for about 55 percent of global warming, but the timing and the degree to which the earth is expected to become hotter are uncertain.