Abe, who plans to present his idea at the Group of Eight summit in Germany in June, said the proposed climate change treaty must be flexible enough to draw all nations' participation.
"Global warming is an issue that should be addressed by the entire world," Abe said at a banquet in Tokyo. "It is indispensable to establish a new framework in which both industrialized and developing countries address this issue together."
The Kyoto Protocol, signed in Japan in 1997, requires some 35 industrialized nations to cut greenhouse gas emissions 5 percent from 1990 levels by 2012. Under the pact, Japan — home to the world's second-largest economy — was required to make a 6 percent cut.
Participation, however, has been limited. The United States refused to join, arguing it would cost millions of U.S. jobs, and objecting that up-and-coming polluters such as China and India were not required to make cuts.
Abe argued that a successor to Kyoto, which expires in 2012, needs to be much broader to have an impact on climate change.
"We must create a new framework which moves beyond the Kyoto Protocol, in which the entire world will participate in emissions reduction," he said.
The proposal also called for more aid to developing nations to boost energy efficiency, technological innovation to reduce emissions, development of renewable energy sources such as solar power, and expansion of nuclear power.
Before the speech, Japanese officials said the 50 percent reduction target was nonbinding and was a general "vision" rather than an ironclad goal.
Indeed, Abe's proposal was short on specifics. It offered no base year from which emissions should be cut. His vow to create a special Japanese fund to help developing countries make cuts included no promises of specific amounts of money.
"We are not trying to tie countries down to a specific position," said Koji Tsuruoka, the Foreign Ministry's director general for global issues.
Japanese officials have expressed reservations about setting specific targets in the early stages of negotiations for fear of discouraging major emitters — such as the United States — from participating.
"I think opinion is divided on whether it is easier to participate by setting a numerical target, or whether it is easier without it," Foreign Minister Taro Aso said earlier this week. "We need to make sure that major emitter nations ... will take part."
Recent climate change discussions have focused on what kind of a pact should follow Kyoto in 2013. Proponents of emission cuts have pushed for discussion of a post-Kyoto pact at the June 6-8 Group of Eight summit in Germany, and a December climate change conference on Indonesia's Bali island.
Abe said the next pact should be flexible, strike a balance between environmental protection and economic growth and promote advancements in low-carbon technologies.
Japan is struggling to meet its Kyoto commitments. The country currently emits 14 percent more greenhouse gases than it did in 1990. The government plans a major overhaul of its emissions reduction campaign to meet its targets.
Still, Japan has made important gains. Energy efficiency has improved by 37 percent the past 30 years, and oil consumption has decreased by 8 percent even though gross domestic product has doubled, Abe said.
Gross domestic product measures the total value of the goods and services a country produces.
Japan's proposal comes amid heightening worldwide concern over climate change, which has already altered bird migrations, brought earlier springs in temperate climate zones and bleached tropical coral reefs with warmer sea water.
Delegates from 120 countries endorsed a report earlier this year, stating the world has the technology and wealth now to act decisively in time to limit a sharp temperature rise that would wipe out species, raise oceans and trigger economic havoc.