The Cabinet will ratify the 1997 Kyoto Protocol on curbing global warming on June 4, Environment Minister Hiroshi Oki said Friday.
The government will submit the necessary documentation to the German-based secretariat by June 6, he added.
On Tuesday, the House of Representatives approved a government proposal to ratify the pact and a bill stipulating measures to achieve Japan's goals under the accord.
The government hopes the House of Councilors will approve both measures next week.
The Kyoto Protocol requires industrialized countries to cut their greenhouse-gas emissions from 1990 levels by an average of 5.2 percent between 2008 and 2012. Under the requirement, which is legally binding, Japan must reduce such emissions by 6 percent.
The Upper House's approval will allow Japan to achieve its goal of ratifying the protocol before June 6, allowing it to go into force by the conclusion of the World Summit on Sustainable Development, to be held in Johannesburg between Aug. 26 and Sept. 4.
The protocol will enter into force 90 days after being ratified by 55 states, which must represent 55 percent of industrialized countries' carbon dioxide emissions in 1990.
Without the United States, which has withdrawn from the pact, ratification by the European Union, Japan, Russia and East European countries is essential to meet the target.
As of May 6, 54 countries, including Romania and the Czech Republic, had ratified the pact. Britain, Germany and the Netherlands have concluded parliamentary procedures for ratification and the EU has announced it will ratify it by June 1.
Japan's greenhouse-gas emissions rose to 6.8 percent above 1990 levels in fiscal 1999, and in 2010 the amount is expected to be 7.4 percent above 1990 figures. In that event, Japan would be obliged to cut emissions by 13.4 percent.