“The president has said from the start that the issue of signing a peace agreement with Japan will be very drawn out in terms of time,” Putin’s spokesman Dmitry Peskov said. “The talks are in their initial stage.”

Tokyo claims the so-called southern Kurils, a string of islands just north of Hokkaido which it calls Northern Territories, as their own.

In the 1950s, the Soviet Union had said it would be willing to transfer Shikotan island and Habomai, a group of islets, to Japan, following a signed peace accord. Japan at the time refused, demanding the entire chain, which also includes the islands of Iturup and Kunashir.

The notion that Moscow could now cede any territory to Japan is extremely sensitive in Russian society, with a number of protests held against it in recent weeks, including in Moscow at the weekend.

Peskov did not rule out the possibility that Putin could hand over territory in exchange for a peace deal.

“Nobody has officially offered anything, so any eventual line of reasoning is hardly appropriate, they don’t help the spirit of the talks,” he said. “Nobody is going to go against their national interests.”

Three of the islands are inhabited while Habomai is a group of islets with only the presence of a border patrol.

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Abe seems to have accepted that continuing to call for the return of Etorofu and Kunashiri could stagnate the ongoing talks and may even dampen the prospect of the two smaller islands being transferred to Japan.

He could face a backlash from his support base with many Japanese deeming the new approach as giving up on Etorofu and Kunashiri, both of which the government has claimed to be an inherent part of Japan’s territory.

After assessing public opinion, Abe is expected to make a final judgment as to whether Japan should strike a deal with Russia on the basis of securing the handover of the two smaller islands.

Abe is seeking a broad agreement with Russia in June when Putin is expected to visit Japan for a summit of the Group of 20 advanced and emerging economies.

During the previous meeting, Abe touched on the 1956 declaration and told Putin that the contents of the document are Japan’s “non-negotiable line”, according to the sources.

Putin is said to have shown an understanding of the proposal.

But it is unclear whether the negotiations would go smoothly as Putin has also suggested that even if the two islands are handed over to Japan, it does not necessarily mean their sovereignty will also be transferred.

The president has claimed the joint declaration does not specify whose sovereignty the two islands would fall under.

In mid-January, Russian Foreign Minister Sergey Lavrov told reporters it would be difficult to make progress in the peace treaty talks without Japan’s acceptance of the outcome of the second world war, including Russia’s sovereignty over the islands.

Lavrov’s remarks following a meeting in Moscow with his Japanese counterpart Taro Kono signalled that Abe may face significant challenges in his summit with Putin.

Security could also be a key topic in the planned talks as Moscow has been concerned that US military troops could be deployed on the islands if they were handed over to Tokyo.

Tokyo and Moscow have promoted confidence-building steps centring on economic cooperation in recent years, making little progress on a peace treaty.

Following the summit, Abe will travel to Switzerland to attend the World Economic Forum in the ski resort of Davos.