Kremlin aide Kirill Dmitriev has proposed rail tunnel under Bering Strait, which would link Russia and US. The envisaged 112-km 'Putin-Trump' tunnel would unlock joint exploration of natural resources and "symbolise unity", Dmitriev remarked. US President Donald Trump said he found the proposal "interesting", while Ukrainian leader Volodymyr Zelenskyy said he "wasn't happy" with the idea.