File photo: Russia's President Vladimir Putin (L) talks to Russian Presidential Aide Yuri Ushakov on the sidelines of the Russia-ASEAN summit in Sochi, Russia, May 19, 2016. REUTERS/Yuri Kochetkov

MOSCOW (Reuters) - Russia wants to boost bilateral ties with Japan on all fronts and hopes to reach a peace treaty with its eastern neighbor, Kremlin aide Yuri Ushakov said on Tuesday, adding however that agreeing a peace treaty needed “scrupulous work.”

Ushakov was briefing reporters before Russian President Vladimir Putin’s visit to Japan later this week.

A territorial dispute between Tokyo and Moscow over a chain of western Pacific islands, seized by Soviet troops at the end of World War Two, has upset diplomatic relations ever since, precluding a formal peace treaty between the two countries.

“The president has already said that our country is not only ready but interested in resolving this long-running problem. ... But we believe this is quite a long process, which requires scrupulous work aimed at boosting trust,” Ushakov said.

He also said the arrest of former Economy Minister Alexei Ulyukayev, who had been deeply involved in bilateral ties with Japan, would not affect dialogue between Moscow and Tokyo.

Ulyukayev was dismissed and put under house arrest in November over allegations he extorted a $2 million bribe from Russian oil producer Rosneft. Ulyukayev denies the charges against him.

Ushakov said that Russian First Deputy Prime Minister Igor Shuvalov had worked on promoting bilateral ties between Russia and Japan, as well as Ulyukayev.