TOKYO - Japan's new energy minister said he aims to expand the nation's electricity feed-in tariff scheme to other energy sources beyond solar power within two years, to help meet the new government's goals to cut greenhouse gas emissions by 25 percent below 1990 levels by 2020.

There are many technical challenges ... but I'd like to do it within two years as much as possible, said Masayuki Naoshima, who was appointed on Wednesday as minister of economy, trade and industry.

Japan's Democratic Party, which took office on Wednesday, has touted a platform to introduce a feed-in tariff for any type of renewable energy supply, under which power companies pay an above-market rate for every unit of such types of power, and boost renewable energy sources to about 10 percent of the country's primary energy supply by 2020.

But Naoshima did not specify the target breakdown for each renewable energy source in 2020.

Solar power is the most costly among clean energy sources in Japan, and is seen as a key green area for fiscal assistance to prompt demand and encourage solar panel makers, such as Sharp Corp, to invest in research and expansion abroad.

There's no need to hurry, but international cooperation is important, Naoshima told a group of reporters, adding that setting up an international greenhouse reduction framework that would involve major emitters such as the United States, China and India, would be indispensable.

Naoshima also said the new government would discuss the introduction of a domestic carbon emissions trading scheme in the fiscal year starting in April 2011.

The Democrats will push for the early passage of a bill that would allow for the set-up of such a trading system.

The party has in the past unsuccessfully submitted similar bills aiming for a 2011/12 introduction. (Reporting by Osamu Tsukimori; Editing by Joseph Radford)