KYIV, May 22 - Russia pressed its offensive in eastern Ukraine on Sunday as Poland’s president traveled to Kyiv to support the country’s European Union aspirations, becoming the first foreign leader to address the Ukrainian parliament since the start of the war.

Lawmakers gave a standing ovation to President Andrzej Duda, who thanked them for the honor of speaking where “the heart of a free, independent and democratic Ukraine beats,” The Associated Press reported. Duda said that to end the conflict, Ukraine did not need to submit to conditions given by Russian President Vladimir Putin.

“Unfortunately, in Europe there have also been disturbing voices in recent times demanding that Ukraine yield to Putin’s demands,” he said. “I want to say clearly: Only Ukraine has the right to decide about its future. Only Ukraine has the right to decide for itself.”

Duda’s visit, his second to Kyiv since April, came as Russian and Ukrainian forces battled along a 551-kilometer (342-mile) wedge of the country’s eastern industrial heartland.

After declaring full control of a sprawling seaside steel plant that was the last defensive holdout in the port city of Mariupol, Russia launched artillery and missile attacks to expand the territory that Moscow-backed separatists have held since 2014 in the region known as the Donbas.

To bolster its defenses, Ukraine’s parliament voted Sunday to extend martial law and the mobilization of armed forces for a third time, until Aug. 23.

President Volodymyr Zelensky has stressed that the 27-member EU should expedite his country’s request to join the bloc. Ukraine’s potential candidacy is set to be discussed at a Brussels summit in late June.

France’s European Affairs minister Clement Beaune on Sunday told Radio J it would be a “long time” before Ukraine gains EU membership, perhaps up to two decades.

“We have to be honest,” he said. “If you say Ukraine is going to join the EU in six months, or a year or two, you’re lying.”

But Poland is ramping up efforts to win over EU members who are more hesitant about accepting Ukraine into the bloc. Zelensky said Duda’s visit represented a “historic union” between Ukraine, which declared independence from the Soviet Union in 1991, and Poland, which ended communist rule two years earlier.

“This is really a historic opportunity not to lose such strong relations, built through blood, through Russian aggression,” Zelensky said. “All this not to lose our state, not to lose our people.”

On the battlefield, Russia appeared to have made slow, grinding moves forward in the Donbas in recent days. It intensified efforts to capture Sievierodonetsk, the main city under Ukrainian control in Luhansk province, which together with Donetsk province makes up the Donbas. The Ukrainian military said Sunday that Russian forces had mounted an unsuccessful attack on Oleksandrivka, a village outside of Sievierodonetsk.

Sievierodonetsk came under heavy shelling, and Luhansk Gov. Serhii Haidai said the Russians were “simply intentionally trying to destroy the city... engaging in a scorched-earth approach.” (ap/ez)