Whether pro-Russian rebels in the east can be brought to heel is still a subject of debate for observers of the long-running conflict.
"As we've seen so many times before, that hasn't been the case. It's a question of whether the separatists in eastern Ukraine are fully under the control of Putin and will abide by this, and if they don't we could see this unraveling quite quickly," Carnell told CNBC's "Worldwide Exchange."
Carnell said a positive outcome of the deal was that it put on ice the U.S. threat of arming Ukraine but, in all, the best perspective on the deal was to be "cautiously optimistic."
Following the deal, Poroshenko said Kiev would reassert control of the joint border with Russia by the end of 2015, adding that the peace deal did not include federalization or autonomy status for pro-Russian rebels.
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Christopher Granville, managing director of the Russia team at emerging market research firm Trusted Sources, agreed that the deal was a "necessary starting point."
"It's not a sufficient condition for a resolution of what is ultimately a geopolitical confrontation going way beyond the horrible events going on in south-eastern Ukraine but it's a necessary condition for getting to a solution," he told CNBC's "Worldwide Exchange."
"But there's chance now that the worst of this violence and the loss of life will be behind us," he added.