The United Nations fears that a US decision to return Yemen's Houthi rebels to a list of terrorist groups could harm the war-torn country's economy, particularly commercial imports of essential items, a senior UN aid official said on Wednesday.The US move, announced last month, takes effect on Friday and hits the Iran-aligned group with harsh sanctions that aim to cut off funding and weapons the Houthis have used in their stepped-up attacks on ships in vital Red Sea shipping lanes.The UN aid operations director, Edem Wosornu, said that while...