The previous proposal had been unacceptable to Japan because it would give Russia more land area, Aso said.
Splitting the land area equally, he said, would give Japan three of the islands and a quarter of the largest, northernmost island, Etorofu.
"We must carry forward negotiations in a sufficiently realistic way"
Japanese foreign minister
"Talking about two islands, three islands or four without taking land area into account is unacceptable," Aso said in response to questions from opposition politicians. "We must carry forward negotiations in a sufficiently realistic way."
He said Japan was keen to see the dispute resolved before the term of Vladimir Putin as Russian president comes to an end in May 2008.
Putin, he said, had expressed a willingness to settle the row.
The dispute has overshadowed relations between Japan and Russia for decades, preventing the two sides from working together on several issues such as exploiting energy resources in the Russian Far East.
Right wing Japanese politicians have insisted that the four islands should be returned to Japan – a proposal that has been repeatedly rejected by Russia.
In late October, shortly after he took office, Shinzo Abe, the Japanese prime minister, told Putin that he wanted to ramp up negotiations over the islands so the two sides can sign a peace treaty.