Russian troops would have an "open road" to capture key cities in eastern Ukraine if they seize control of Bakhmut, Ukrainian President Volodymyr Zelenskyy warned in an interview with CNN, as he defended his decision to keep Ukrainian forces in the besieged city.

"This is tactical for us," Zelenskyy said, insisting that Kyiv's military brass is united in prolonging its defense of the city after weeks of Russian attacks left it on the cusp of falling to Moscow's forces.

"We understand that after Bakhmut they could go further. They could go to Kramatorsk, they could go to Sloviansk, it would be open road for the Russians after Bakhmut to other towns in Ukraine, in Donetsk direction," he told CNN's Wolf Blitzer in an exclusive interview from Kyiv.

The TV channel said "a weeks-long assault from Wagner mercenary troops, which has picked up pace in recent days, has forced thousands from the city and decimated its infrastructure. But Ukrainian troops have also mounted a dogged defense of the area, stalling Russia's progress."

Zelenskyy said his motivations to keep the city are "so different" to Russia's objectives. "We understand what Russia wants to achieve there. Russia needs at least some victory – a small victory – even by ruining everything in Bakhmut, just killing every civilian there," Zelenskyy said.

He said that if Russia is able to "put their little flag" on top of Bakhmut, it would help "mobilize their society in order to create this idea they're such a powerful army."