Russian lawmakers pushed through the final procedural steps needed to annex Ukrainian territory on Tuesday despite Moscow not fully controlling any of the four regions it claims.
Legislation to annex four Ukrainian regions was approved by the upper house of parliament.
Russia's lower house voted on Monday in favor of annexation, following a series of referendums in the region that the international community denounced as illegitimate.
The annexation process will be completed when the documents are returned to Putin for final approval.
Even though it does not fully control any of the four regions it seeks to claim, Moscow is still trying and Ukrainian forces have made gains in retaking territory.
Both Ukrainian officials and the leader of the region confirmed that Ukrainian troops broke through Russian defenses on Monday.
The southern advance, which accompanies efforts to advance and reclaim territory in the east, is said to be targeting supply lines that serve as many as 25,000 Russian troops.
In the last few weeks, Kyiv has made significant progress on the battlefield and handed a number of humiliating defeats to the Russians. Russian troops were forced to retreat a day after Putin claimed the city as Russian after it was reclaimed by the Allies. Ukrainian President Volodymyr Zelensky said on Monday that the military had taken back many towns.
Russia is trying to claim something as its own. The claim that the regions of Donetsk, Luhansk, Kherson and Zaporizhzhia make up 18% of Ukrainian territory is not clear. Moscow claimed to have annexed all of the regions it did not. As Ukrainian counteroffensives grind on, the Kremlin has refused to clarify where Russia's new borders will actually be. Moscow is conducting consultations in the Zaporizhzhia and Kherson regions to determine borders, according to the Kremlin.
The Ukrainian counteroffensives appear to be part of a larger plan.
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There are signs of disarray in Russia's retreat on the Ukrainian fronts.