WATCH: Pentagon calls Zelenskyy’s leadership ‘key aspect’ to Ukraine defense

Pentagon press secretary Pat Ryder on Tuesday described Ukraine’s president Volodymyr Zelenskyy as a “key aspect” in the country’s resistance to Russia after the Ukrainian leader met with troops in the eastern city of Bakhmut, the scene of some of the most intense combat since the country was invaded.

Watch the briefing in the player above.

“Broadly speaking we continue to see his leadership be a key aspect in Ukraine’s fight,” Ryder said.

While in Bakhmut, Zelenskyy praising the Ukrainian troop’s “courage, resilience and strength” as artillery boomed in the background.

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Zelenskky met with military personnel in a dimly lit building — possibly a disused factory — in Bakhmut, which he has called “the hottest spot on the entire front line,” his office said. The city, about 600 kilometers (380 miles) east of Kyiv, has remained in Ukrainian hands, thwarting Moscow’s goal of capturing the rest of Donetsk province and the entire Donbas industrial region.

The Ukrainian leader told the troops he passed through Sloviansk, Kramatorsk and Druzhkivka to reach Bakhmut in an unannounced trip that appeared designed to show Moscow’s failure to capture the city and dishearten the Russians trying to surround it.

“Bakhmut Fortress. Our people. Unconquered by the enemy. Who with their bravery prove that we will endure and will not give up what’s ours,” he wrote on his Telegram channel, thanking the troops for “the courage, resilience and strength shown in repelling the enemy attacks.

“Since May, the occupiers have been trying to break our Bakhmut, but time goes by and Bakhmut is already breaking not only the Russian army, but also the Russian mercenaries who came to replace the wasted army of the occupiers,” he said.

Russia’s invasion, which began Feb. 24, has lost momentum. The illegally annexed provinces of Donetsk, Kherson, Luhansk and Zaporizhzhia remain fiercely contested. Capturing Bakhmut would sever Ukraine’s supply lines and open a route for Russian forces to press on toward cities that are key Ukrainian strongholds in the Donetsk province.

Mercenaries from the Wagner Group, a shadowy Russian military contractor, are reported to be leading the charge in Bakhmut. Before Russia’s full-scale invasion, Russia-backed separatists had controlled parts of Donetsk and neighboring Luhansk since 2014. The two provinces together make up the Donbas.

Unverified videos on a popular Russian social media platform showed the Wagner Group’s leader, Yevgeny Prigozhin, standing near an artillery piece and saying he was ready to meet Zelenskyy in Bakhmut. In a statement accompanying the videos, Prigozhin’s spokespeople relayed a message to Zelenskyy reading: “If you haven’t left Bakhmut yet, I’m ready to meet you. Prigozhin.” It wasn’t clear from the videos where they were shot or when.