Ukrainian President Volodymyr Zelensky said Wednesday he would not "sell" his country in any deal with the United States for access to Ukraine's critical resources.

Kyiv and Washington had been in talks on a deal to give the US preferential access to vast amounts of the war-torn country's natural resources and critical minerals.

President Donald Trump cast the deal as compensation for support already delivered under the Joe Biden administration.

Zelensky rejected it, saying it lacked concrete security guarantees for Ukraine -- Kyiv's key demand from its Western backers ahead of any ceasefire talks with Moscow.

"I am defending Ukraine, I cannot sell our country. That's all," he said on Wednesday about the failed deal.

He also accused the United States of not engaging in a "serious conversation," and said he was ready for further negotiations.

"I say again that we are ready for a serious document. We need security guarantees."