Ukrainian President Volodymyr Zelensky said the Russian army would have an "open road" into eastern Ukraine if it captures the besieged city of Bakhmut, US media reported Tuesday.

"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 the Donetsk direction," he told CNN's Wolf Blitzer in an interview due to broadcast in the United States on Wednesday.

The Russian army has vowed to capture Ukraine's eastern town of Bakhmut, a symbolic prize in months of fierce combat, as a precursor for offensives deeper into Ukraine.

The battle for Bakhmut -- a salt-mining town with a pre-war population of 80,000 -- has been the longest and bloodiest in Russia's more than year-long invasion that has devastated swathes of Ukraine and displaced millions.

Russia has appeared intent to capture the town at all costs.

"Capturing (Bakhmut) will allow for further offensive operations deep into the defence lines of the Armed Forces of Ukraine," Russian Defence Minister Sergei Shoigu told military officials during a televised meeting on Tuesday.

Zelensky told CNN that his armed forces were resolved to stay in Bakhmut.

"I had a meeting with the chief of staff yesterday and the chief military commanders online and offline ... and they all talk that we have to stand strong in Bakhmut," he said.

"Of course, we have to think about the lives of our military. But we have to do whatever we can whilst we're getting weapons, supplies and our army is getting ready for the counter-offensive."