Japan needs to move beyond simply showing leadership and come up with ambitious targets on cutting its carbon gas emissions, U.N. climate chief Yvo de Boer said Friday.

Six options for the nation's midterm emission cuts, ranging from a 7 percent increase to a 25 percent reduction by 2020 compared with 1990 levels, were unveiled Thursday by a study team under Prime Minister Taro Aso.

"It is not my responsibility to set the Japanese target," de Boer told a news conference in Tokyo, stressing, however, that industrialized countries need to reduce their emissions by 25 percent to 40 percent by 2020 to prevent serious damage to the global climate.

Japan, which played a key role in organizing the Kyoto Protocol, is lagging far behind its goals set under the treaty and is unlikely to meet its 6 percent emissions cut by 2010 based on the fiscal 1990 level.

Noting there are only 296 days left until governments gather at Copenhagen to agree on a long-term goal to curb environment change, the climate expert said crafting a new treaty will not be easy.

"I am sure that Prime Minister Aso is confident that Japanese businesses and societies are committed to addressing the issue," said de Boer, expressing hope that Japan's attitude has changed. He was in Tokyo to attend an informal two-day session to discuss global carbon emissions targets beyond 2012.

A Foreign Ministry official said earlier in the day that the two-day session made no breakthrough agreements, but saw "a forward-looking attitude" by both developed and developing countries.