KYIV, June 21 (Aljazeera) - Ukraine’s counteroffensive against Russian forces has been “slower than desired”, but Ukrainian forces will not be pressured into speeding up, the country’s President Volodymyr Zelenskyy has said, while Russian President Vladimir Putin said Moscow had observed a “lull” in Kyiv’s campaign.

Ukrainian forces are being slowed in their advance by vast minefields laid by Russian forces, Zelenskyy told to the United Kingdom’s BBC in an interview on Wednesday. With some 200,000 square kilometres (more than 77,000 square miles) of Ukrainian frontier territory littered with Russian land mines, the Ukrainian leader said that “at stake is people’s lives”.

“Some people believe this is a Hollywood movie and expect results now. It’s not,” Zelenskyy told the BBC.

“Whatever some might want, including attempts to pressure us, with all due respect, we will advance on the battlefield the way we deem best,” he said.

Confirming that Ukrainian forces had retaken eight villages in the south and east of the country, Zelenskyy also said that Ukraine would never negotiate while Russian forces remain on Ukraine’s territory and that the conflict would not be allowed to stagnate.

“No matter how far we advance in our counteroffensive, we will not agree to a frozen conflict” which would be “a prospectless development for Ukraine”, he said.

Zelenskyy’s interview with the BBC coincided with a conference in London where allies pledged billions of dollars in economic and reconstruction aid, and on a day when Russia’s leader again said that Ukraine’s counteroffensive was faltering.

In televised remarks on Wednesday, Putin said that Kyiv had sustained serious military losses since beginning its push earlier this month to retake territory held by Russian forces, and a “certain lull” had been observed by Moscow on the front lines in Ukraine.

Contradicting the Russian president’s view of the conflict, the chief of Russia’s Wagner mercenary force, Yevgeny Prigozhin, accused Russian defence officials on Wednesday of not telling the truth about the progress of Ukraine’s counteroffensive.

Moscow was losing territory to Ukrainian forces, Prigozhin said, and Russian defence officials were hiding the truth.

“They are misleading the Russian people,” Prigozhin said in an audio message released by his spokespeople.

A number of villages have been lost and Russian troops are suffering from a lack of arms and ammunition, he said.

“Huge chunks have been handed over to the enemy,” Prigozhin said, warning that Ukrainian troops had already sought to cross the Dnipro river, a natural border on the front line.

“All of this is being totally hidden from everyone,” the Wagner chief said. “One day Russia will wake up to discover that Crimea too has been handed over to Ukraine,” he added.

The Washington, DC-based Institute for the Study of War (ISW) said on Thursday that Russian sources had noted a “relatively slower pace of Ukrainian offensive operations” in the west of the Donetsk and Zaporizhia regions in recent days. However, the ISW said that Ukraine had long indicated that its counteroffensive would be a “series of gradual and sequential offensive actions”.

Military analysts believe that Kyiv’s major counteroffensive operations have not yet started.

“The success of Ukrainian counteroffensives should not be judged solely on day-to-day changes in control of terrain,” the ISW said.

“The wider operational intentions of Ukrainian attacks along the entire front line may be premised on gradually degrading, exhausting, and expending Russian capabilities in preparation for additional offensive pushes,” it said.

In his daily, late-night address on Wednesday, Zelenskky said that Ukrainian forces were “destroying the enemy” in the south of the country and making advances. In the east, “our defences are firming”, he said.

“And I am especially grateful, guys, for every shot down Russian helicopter … Each [shot] is important,” he said.