1022 GMT - Corn contracts rise to their highest levels since July 2023 amid concern around pressures in the Black Sea and lower-than-expected U.S. yields. "U.S. corn estimates pointed to lower corn yields, while continued attacks in the Black Sea disrupted exports," Rabobank analysts write. U.S. agricultural group Pro Farmer estimated Friday the 2026 U.S. corn crop will come in at 15.344 billion bushels amid inconsistent field performance, with yields at their lowest level since 2020. Meanwhile, Ukrainian President Volodymyr Zelensky said Russia refused a truce that would halt attacks against ships carrying grains through the Black Sea. Front-month corn contracts jump 2.65% to $5.22 a bushel, up around 26% from the contract's June lows.