Washington has brandished a proposed Black Sea ceasefire as evidence the Trump administration can shift the dial in Russia's war on Ukraine but Kyiv and its allies may be wary Russian President Vladimir Putin could emerge from the deal with the upper hand.After three days of talks in Saudi Arabia involving American, Ukrainian and Russian delegations, Secretary of State Marco Rubio said that the U.S. was evaluating Russia's terms after Moscow agreed 'in principle' to a ceasefire deal. These include ending the use of commercial vessels for military purposes but the Kremlin wants sanctions to be lifted in return.But two