The United States has frozen its financial contributions to a United Nations fund for a multinational security support mission in Haiti, a UN spokesperson said on Tuesday, a move that would stop $13.3 million in pending aid."We received an official notification from the US asking for an immediate stop work order on their contribution" to the trust fund for the Multinational Security Support (MSS) mission, said Stephane Dujarric, the UN secretary-general's spokesperson, referring to the already u