What was the US proposal regarding Ukraine's resources, and why did President Zelensky reject it?

The US proposed a deal for 50% of Ukraine's mineral wealth, possibly extending to natural resources including oil and gas. This offer was characterized as seeking reimbursement for American support already provided to Ukraine, with National Security Adviser Mike Waltz stating Americans deserve payback for their investment in the war. President Zelensky rejected the deal because it lacked security guarantees. Ukrainian officials noted that while some profits would be reinvested into post-war reconstruction, Zelensky considered security assurances essential, especially given Ukraine's previous experience when Western security promises following nuclear disarmament weren't fulfilled.