Japan will fail to meet its Kyoto protocol targets for reducing greenhouse gases unless it buys a large quantity of emissions credits from other countries, according to analysts and diplomats, underlining the credibility problems of the unratified international treaty.

Japan, where the protocol was drawn up in 1997, has been seen as crucial to the success of the agreement, which has not been ratified by the US. Japan is committed to cutting average greenhouse gas emissions by 6 per cent from 1990 levels in the period 2008-2012, but is currently emitting about 10 per cent more than it did in 1990.