Ukraine said its military made some progress gradually pushing Russian forces away from the city of Kharkiv as fighting in the east and south of the country continues and the United States warned that Russian President Vladimir Putin is preparing for a long war.

Ukraine’s natural-gas pipeline operator said that beginning May 11 it would stop Russian shipments through its key Novopskov hub in the east in an area controlled by Moscow-backed separatists.

It said the hub handles about one-third of Russian gas passing through Ukraine to Western Europe. Russia’s state-owned natural gas giant Gazprom put the figure at about one-quarter.

President Volodymyr Zelenskiy said on May 10 that Ukrainian successes pushed Russian forces out of four villages around Kharkiv, which has been under bombardment since the war began.

“But I also want to urge all our people…not to spread excessive emotions. We should not create an atmosphere of excessive moral pressure, where victories are expected weekly and even daily,” Zelenskiy said in a video address.

In the strategic southern port of Mariupol, Russian forces continued their assault on the Azovstal steel plant where the city’s last defenders are holed up. An aide to the mayor said at least 100 civilians were still trapped there.

Russia is trying to reinforce exposed troops on Snake Island, which could enable it to dominate the northwestern Black Sea with strategic air-defense and coastal defense cruise missiles, the British Ministry of Defense said in a regular bulletin.

“Ukraine has successfully struck” Russian air defenses and resupply lines in the Black Sea with drones, the bulletin noted, leaving Russian resupply lines exposed after the Russian Navy retreated to Crimea following what the United States says was the sinking of the Moskva missile cruiser by Ukraine last month. Ukraine has not confirmed the attack.

Russian missile strikes also hit the southern port of Odesa in an apparent effort to disrupt supply lines.