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"The Duma's request that Vladimir Putin recognises the Ukrainian regions of Donetsk and Luhansk as independent shows flagrant disregard for Russia's commitments under the Minsk agreements," British Foreign Secretary Liz Truss said.
The agreements, named after the Belarusian capital where they were agreed to in 2014 and 2015, sought to halt the war between the Ukrainian government and the secessionists, and are the only framework for resolving the conflict peacefully.
"If this request were accepted, it would represent a further attack on Ukraine's sovereignty and territorial integrity, signal an end to the Minsk process and demonstrate a Russian decision to choose a path of confrontation over dialogue," Ms Truss said.
Russia's Parliament, the Duma, voted on Tuesday to urge Mr Putin to recognise the independence of the two Ukrainian separatist regions, amid tensions with the West over Moscow's troop build-up near by.
Russia has issued passports to hundreds of thousands of residents of the separatist-held enclaves, where Ukrainian government troops have been battling insurgents in a conflict that has claimed more than 14,000 lives since 2014.
The Duma proposal prompted strong condemnation from the US on Wednesday, with Secretary of State Antony Blinken saying it would "constitute a gross violation of international law".
Meanwhile In Kiev, Ukrainian Foreign Minister Dmytro Kuleba warned that if Russia moved to recognise the rebel territories, "Russia de facto and de jure will withdraw from the Minsk agreements with all the attendant consequences".
But at a heated UN Security Council meeting earlier on Thursday, Russian deputy foreign minister Sergey Vershinin blamed the current crisis on Kiev's alleged breaches of the ceasefire agreement reached in the accords.
"Ukraine stubbornly refuses to implement the provisions of the Minsk agreements," he told the Council, accusing Kiev of repeated attacks on the region affecting "thousands of victims".