"Taking into account of situations surrounding North Korea, we have decided that we need to keep the sanctions".
Six-party talks, including Japan and the North, have stalled pending Pyongyang's full accounting of its nuclear activities.
Its declaration was due at the end of 2007.
The talks, aimed at curbing the North's nuclear ambitions, also include the US, South Korea, Russia and China.
Christopher Hill, the US envoy, said earlier this week that the US and North Korea have made progress but no breakthrough in the prolonged negotiations.
Hill met Kim Kye Gwan, his North Koran counterpart, in Singapore earlier this week.
North Korea has been offered energy and economic aid in return for nuclear disarmament steps.
Machimura also reiterated that Tokyo would not forge diplomatic ties with Pyongyang unless the row over the North's abduction of Japanese nationals can be resolved.
The highly emotive issue in Japan concerns Japanese citizens taken against their will to North Korea to help train spies their in language and custom.
North Korea admitted in 2002 that its agents had abducted 13 Japanese.
Five of them were repatriated that same year, but Pyongyang says the other eight are dead.
Tokyo wants more information about the eight and four others it says were also kidnapped, as well as demanding that any survivors are sent home.
Meanwhile, activists said on Friday that a group of North Korean refugees detained in Thailand have launched a hunger strike.
The 12 men and 17 women from North Korea stopped eating on Thursday and were demanding they be sent to the US, Chun Ki-won, a reverend and head of Seoul-based missionary group Durihana Mission, told the Associated Press news agency.
The hunger strikers included a female North Korean cancer patient at a hospital in Thailand, Chun said.
He said 17 of the hunger striking refugees were being held in a Thai immigration detention facility, while the other 11 are being housed elsewhere in Thailand.
During recent years, thousands of North Koreans have made the long and risky land journey through China to Southeast Asian countries to seek asylum elsewhere, usually in South Korea.