Russian President Vladimir Putin may not have long to wait for the first major test of his decision to annex a swathe of Ukraine, with Kyiv’s forces threatening to encircle a pocket of the Donbas region he set out to conquer.

The Kremlin said Putin will on Friday sign what it called treaties with the Moscow-anointed leaders of four partially occupied provinces in Ukraine’s east. Ratification of their absorption into Russia would soon follow.

The move would follow this month’s illegal and hastily conducted referenda in those territories on whether to join Russia. Yet even as Putin prepares for a significant escalation of the conflict, Ukrainian, Western and Russian military analysts say Russian units are at risk of being enveloped in the Donetsk town of Lyman.