Japan has told Russia it will not be satisfied with the return of just two of the four disputed Kuril islands.
Koizumi restated Japan's claim to the Kuril islands in September
Russia's Foreign Minister Sergei Lavrov suggested at the weekend that Moscow might return two of the islands.
Japanese Prime Minister Junichiro Koizumi said on Tuesday Tokyo would insist that all four islands seized by Soviet troops in 1945 be returned.
The long-running dispute has prevented both sides from formally declaring an end to World War II hostilities.
A Japanese government spokesman said Tokyo was hoping to discuss the dispute during the Asia-Pacific Economic Co-operation summit in Chile later this week.
"If the two leaders [Mr Koizumi and Russian President Vladimir Putin] have a chance to meet, I think they will discuss the issue there," said Chief Cabinet Secretary Hiroyuki Hosoda.
However Mr Koizumi said on Tuesday that "Japan cannot be content" with the return of just two of the islands .
"We maintain the policy of concluding a peace treaty only after
clarifying who owns the four the islands," he told reporters.
The three islands and a cluster of outcrops are currently inhabited by a small community of Russian fishermen and their families.
Mr Koizumi recently restated his country's claim to the territory, known in Japan as the Northern Territories and in Russia as the southern Kurils.
Moscow's offer is based on a promise by former Soviet leader Nikita Khrushchev, made in 1956, to return two of the islands - a pledge that was never fulfilled.
In a Russian television interview, Mr Lavrov said the present Russian government should live up to the commitment.
"We acknowledge this declaration, but its realisation requires a dialogue," he said.
"No one has ever discussed how to perform this in practice."
Lavrov's statement was considered in Russia as an attempt to probe public opinion on the issue. Earlier this month Russia settled a territorial dispute over several river islands on its border with China.