(Bloomberg) -- Russian lawmakers overwhelmingly backed a tougher stance on territorial concessions in line with the country’s recently revised constitution, dealing a blow to Japanese Prime Minister Shinzo Abe’s hopes of resolving a festering dispute over four islands that dates back to World War II.

A bill that equates surrendering Russian territory to extremism passed the first of three required readings in the State Duma lower house of parliament by 382 votes to 0 against on Tuesday. The draft law must be approved in both houses of the legislature before being submitted for President Vladimir Putin’s signature.

State Duma Speaker Vyacheslav Volodin, a top Putin ally, said Russia wouldn’t hesitate to use the measure to detain or seek the extradition of any foreigner who calls for Russia to cede part of its territory.

Putin in 2014 annexed Ukraine’s Crimean peninsula, which historically belonged to Russia but was transferred to Ukraine when they were both part of the Soviet Union. The U.S. and European Union imposed sanctions in retaliation. Abe and Putin have met 25 times since 2012 to try to resolve the dispute over four islands known as the South Kurils in Russia and the Northern Territories in Japan that were seized by Soviet troops in the dying days of World War II.

The dispute has prevented the two sides from signing a peace treaty formally ending the war. While Putin and Abe agreed in 2018 to negotiate on the basis of a 1956 declaration under which the Soviet Union would return two islands following a peace accord, there has been little recent progress.

Constitutional changes confirmed in a July 1 referendum made it illegal to hand over any part of Russia, though the new basic law does allow delimitation, demarcation or re-demarcation of borders.

Despite this exemption clause, public opinion in Russia has hardened against even minor territorial concessions, said James Brown, an expert on Russo-Japanese ties at Japan’s Temple University.

“Putin has made it politically impossible for these islands to be handed over,” Brown said in a commentary published by the London-based Royal United Services Institute.

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