White House officials said yesterday that President Bush had still not settled on details. But a report on the economy published by the White House yesterday spelled out its philosophy on the contentious issue of limiting emissions of gases linked to global warming.

In contrast to the hard targets and short timetable in the 1997 treaty, the Kyoto Protocol, the administration's policy calls for technology and incentives that would lead to a decades- long decline in emissions, according to officials involved in the policy debate and experts consulted by the administration.

Pressure has been rising on Mr. Bush to come up with specifics as the Senate develops bills aimed at controlling power-plant emissions — including carbon dioxide, the main gas that traps heat in the atmosphere, warming Earth like a greenhouse.

The president is planning to visit Asia late next week, and Japan is eager to see some indication of climate policy in view of Mr. Bush's rejection of the Kyoto Protocol.

While most nations have endorsed it, few have ratified it. Japanese officials have said they will be most likely to pursue ratification if they see signs that the United States may eventually act to limit warming.

The administration's approach is described in six pages of the 440- page Economic Report of the President, released by the White House Council of Economic Advisers.

"The uncertainty surrounding the science of climate change suggests that some modesty is in order," it reads. "We need to recognize that it makes sense to discuss slowing emission growth before trying to stop and eventually reverse it." (The report is available on the Web at www.whitehouse.gov/cea/pubs.)

The report also discusses the merits of measuring countries' production of greenhouse gases against their economic production. This reflects Mr. Bush's first speech on climate change, in June, in which he admitted that the United States is by far the biggest source of greenhouse gases (about 20 percent of the total) but defended that rate as a reflection of the country's enormous output of goods and services (about 25 percent of the world's total).

In a speech in December, R. Glenn Hubbard, chairman of the Council of Economic Advisers, said the science remained too equivocal to pursue "a premature Kyoto-style agreement."

The report yesterday echoed that theme: "The current uncertainty surrounding climate change implies that a realistic policy should involved a gradual, measured response, not a risky, precipitous one."

Many environmental groups and economists have called for limits on emissions, combined with a system that allows companies to exceed the caps by "trading" with other companies. For example, a power company that emits carbon dioxide might buy credits from a paper company that is growing forests, which absorb carbon dioxide.

The administration has long been divided over such a system, with some cabinet members and senior White House officials favoring it and others, led by Vice President Dick Cheney, strongly opposed.

The new document said such a system sometimes made sense, pointing to the trading system for reducing sulfur releases linked to acid rain. But it also said greenhouse gases would be much more difficult to measure, monitor and trade. "It would be dangerous to make any serious U.S. policy or commitment dependent on newly designed and untried international institutions," the report said.

Some environmental groups challenged assertions in the document. The World Resources Institute, for instance, said setting emission rates as a percentage of economic growth would never reduce overall emissions, only slow their increase.

But Dr. John M. Reilly, an economist at the M.I.T. Joint Program on the Science and Policy of Global Change, who analyzed various scenarios for the White House, said the general approach made sense.

"Starting slow and building up is a well-established economic idea," Dr. Reilly said. "You don't want to suddenly shock the economy by saying you have to reduce by 30 percent tomorrow."

Under the Kyoto plan, by 2012 the United States would have had to cut emissions of carbon dioxide and other gases to roughly 30 percent below projected levels.

But in the absence of stringent requirements, Dr. Reilly said, the government needs to offer strong incentives if companies are to seek out innovations that might solve the problem. In the end, he said, some limit on emissions must be set if emissions are to drop.

As he put it, "The basic story is, if a problem is going to solve itself, then it's not a problem."