Japan will have to impose carbon taxes and other tough measures on the industrial sector to meet its long-term goals of reducing greenhouse gas emissions, the environment minister said Wednesday.

Ichiro Kamoshita, who will host a meeting of environment ministers from top industrialized countries this coming weekend, said such steps could even come sooner if it appears Japan won't meet its Kyoto Protocol reduction targets. Japan is struggling to meet obligations under the Kyoto global warming pact to cut emissions of greenhouse gases by 6 percent below 1990 levels by 2012.

Japan's industrial sector currently faces only voluntary restrictions on emissions. Kamoshita said policy choices included a carbon tax on emissions and a so-called "cap-and-trade" system under which companies or industries buy and sell the rights to pollute beyond mandatory limits.

"If there are indications that we're not going to achieve that 6 percent, then earlier rather than later, we're going to consider and introduce various methods," Kamoshita told reporters.