Soldiers of the Ukrainian army on the front line during the Joint Forces Operation in Donbass area, Luhansk region, Ukraine, on June 2018.

A high-profile prisoner exchange between Russia and Ukraine is being seen as a boost to the possible resumption of peace talks, but some experts are tempering those hopes.

Ambassador Kurt Volker, the U.S. special representative for Ukraine negotiations, told CNBC Wednesday that "there is a long way to go before there would be any normalization between the two countries."

"Russia's invasion, occupation, and claimed annexation of Crimea will never be accepted by Ukraine," Volker, who is also the executive director of the McCain Institute for International Leadership, told CNBC. "That said, it is possible to make progress toward peace in Eastern Ukraine."

"This prisoner exchange is a good step, that could pave the way for further exchanges, a more durable cease-fire, withdrawal of heavy weapons and — ideally — a decision by Russia to proceed with implementing the Minsk agreements. If so, it would tremendously improve the lives of the local population," he added.

On Saturday, a possible thawing of frosty relations between the two neighbors came about after Russia and Ukraine exchanged a total of 70 prisoners, including Ukrainian sailors that were detained in November 2018 following a skirmish in the Kerch Strait.

The incident in the strait was just one of a number of incidents reflecting heightened tensions between the countries since 2014, following Russia's annexation of Crimea and its role in a pro-Russian uprising in the Donbass region in the east of the country.

The uprising prompted Russian-backed separatists within the Donbass to proclaim two "people's republics" in Donetsk and Luhansk, exacerbating the destabilization of (and tensions with) Ukraine. It has also led to Russia becoming something of a pariah in the international community and it is still subject to sanctions for its actions.