Prime Minister Junichiro Koizumi has rejected a request from Thailand to scrap Japanese import tariffs on rice as part of a free-trade agreement, the farm minister said Tuesday.

"What is impossible is impossible, even if a lot of time is spent on it," Yoshinobu Shimamura quoted Koizumi as telling Thai Prime Minister Thaksin Shinawatra during their chat on the sidelines of a summit of the Asia-Europe Meeting on Friday in Hanoi.

The minister of agriculture, forestry and fisheries also told a regular news conference that Japan has no future plans to agree to remove rice tariffs.

"It is important to maintain the country's food self-sufficiency ratio," Shimamura said.

Thaksin indicated in the meeting that Bangkok would put off its request to remove the politically sensitive import tariffs on rice, according to Shimamura.

Thaksin was quoted as saying that Bangkok wants to promote FTA negotiations with Japan and that it will take time to deal with difficult issues.

Koizumi responded that the two countries should exclude difficult issues from the FTA discussions.

Japan and Thailand aim to conclude their negotiations by the end of this year, but Tokyo is facing big challenges over Bangkok's requests that Japan open up its labor market and scrap import tariffs on rice, chicken, sugar and starch.