BONN, Germany (AP) - With a deal finally reached on implementing the 4-year-old Kyoto Protocol to combat climate change, ministers and environmentalists are expressing relief.

But much remains to be done before its rules become reality.

A 48-hour session reaching well into Monday saved the accord, which appeared close to collapse under Japanese opposition to binding sanctions for violators of the treaty.

Those were dropped as nations pushed to avoid a repeat of last November's failure in The Hague, Netherlands, to agree on rules for reducing industrial pollution.

``Nobody wanted a failure,'' said Michael Zammit Cutajar, the top U.N. official dealing with climate change. ``The deadline really bit this time.''

With environment ministers gone, experts from 178 countries will spend the rest of this week hammering out technical details to back up the political agreement, which clears the way for more nations to ratify the protocol.

``We made a tremendous political advance today,'' Cutajar said Monday. ``If there's sufficient confidence,'' the next U.N. climate conference in Marrakesh, Morocco, in October could ``start to look ahead beyond the issues that we have been dealing with now,'' he added.

To take force, the accord must be ratified by 55 countries responsible for 55 percent of global greenhouse gas emissions, blamed for heating up the atmosphere. The 30 nations that so far have ratified the protocol include none of the world's largest industrial powers.

Monday's outcome still left Tokyo's intentions on ratifying the treaty unclear and the United States - the world's leading producer of greenhouse gases - no closer to rejoining it.

President Bush rejected the pact in March, calling it flawed and harmful to the U.S. economy.

On Tuesday, Secretary of State Colin Powell reaffirmed that the protocol was not acceptable to the United States. He said the United States has a good record on environmental issues and wasn't shirking its responsibilities to help reduce greenhouse gases.

``We are committed to working with all nations of the world to find a consensus in the near future,'' Powell said. ``Hopefully, we can present some new ideas.''

Powell spoke to reporters in Tokyo after negotiators in Bonn, Germany, ignoring U.S. objections, agreed on rules for combatting these emissions.

Japanese Environment Minister Yoriko Kawaguchi hailed the Bonn agreement as a ``vital step forward toward realizing the entry into force of the Kyoto Protocol.'' But she stressed that ``the widest possible participation'' is needed, reflecting Japan's ambiguity on whether it will push ahead with ratification if Washington stays out.

``The future of the protocol now very much depends on what Japan does,'' said Bill Hare of the environmental group Greenpeace. ``It's now time for Japan to come clean on its intentions, to move forward and ratify the protocol without delay and without the United States.''

Delegates negotiated over financing, emission credits for forests soaking up carbon dioxide, mechanisms for offsetting pollution reduction targets as well as sanctions.

In a major concession by the European Union, the accord allows countries to offset their obligations to reduce industrial pollution by counting the proper management of forests and farmlands that absorb carbon dioxide, known as carbon ``sinks.''

Environmental groups said the allowance for sinks effectively reduced the commitment in the Kyoto accord to cut emissions by 5.2 percent from their 1990 levels.

``This agreement here will probably permit, if all the loopholes are used, emissions to increase rather than decrease,'' Hare argued. ``In environmental terms, it's a lost opportunity.''

European officials conceded the deal was weaker than they had hoped, but insisted that making concessions was a worthwhile price to pay.

The chief EU negotiator expressed optimism that the agreement would prompt Washington to reconsider. ``The discussion should be easier now that the United States sees that the Kyoto Protocol is going ahead,'' said Belgian Energy Minister Olivier Deleuze.

There was no immediate sign of a change of heart from Washington.

``This does not change our view the Kyoto Protocol is not sound policy,'' U.S. delegation leader Paula Dobrianksy told delegates.