Japan has slashed its carbon dioxide emissions reduction target.

Japan says it now tentatively aims to reduce its greenhouse gas emissions by 3.8 percent from fiscal 2005 levels by 2020 instead of the 25 percent cut from 1990 levels as promised in 2009.

The announcement Friday from the world's fifth-largest emitter of carbon dioxide struck a blow to the United Nations' Nov. 11-22 climate talks in Warsaw, Poland.

"I don't have any words to describe my dismay," Xinhua News Agency quoted China's negotiator in Warsaw, Su Wei, as saying about the downwardly revised air pollution goal.

Japan's environment minister, Nobuteru Ishihara, said the new target "does not consider the possible effect of nuclear power plants reducing emissions" and that Japan "would set a more definite target" after it decided which sources of energy it would use in the future, The New York Times reports.

All 50 of Japan's working reactors remain offline, pending safety checks after the March 2011 Fukushima nuclear power plant disaster triggered by a massive earthquake and tsunami.

A poll by Japan's Fuji TV in October revealed 60 percent of 1,000 respondents oppose restarting the country's nuclear power plants, even if they were confirmed by authorities as adhering to new, stricter regulations.

Ishihara said the new target assumes Japan will achieve energy savings of about 20 percent by investing in renewable energy sources and energy-efficient technology.

Prior to the Fukushima disaster, nuclear had provided about 30 percent of Japan's electricity, with renewable energy accounting for less than 3 percent, excluding hydropower. Japan now relies more on coal- and gas-fired power and has become the world's largest importer of liquid natural gas.

Reacting to Japan's reduced target announcement, Christiana Figueres, executive secretary of the U.N. Framework Convention on Climate Change, said, "My hope is that Japan understands that investment in renewable energies galvanizes investments and creates new jobs."

Greenpeace said that based on the environmental group's calculations, Japan still could achieve emissions reductions of more than 20 percent without nuclear power if it more aggressively pursued renewable energy.

"Japan can get dramatic emission reductions while shutting down nuclear entirely," Martin Kaiser, head of the Greenpeace delegation to Warsaw, was quoted as saying by The Wall Street Journal.

Japan also said it would provide $16 billion through 2015 to help developing countries curb their greenhouse gas emissions.

Still, Kelly Dent, climate change representative for aid and development charity Oxfam told the British newspaper The Guardian, "Japan's dramatic U-turn on its emissions target commitments is a slap in the face for poor countries who are right now struggling to cope with changes to their climate, and who will face yet more extreme and unpredictable weather in the future."