March 30 (Reuters) - Speculators switched to a net long position in cotton futures and options on ICE Futures U.S. for the first time in five weeks betting on nearby supply tightness, U.S. Commodity Futures Trading Commission data for the week to March 28 showed on Friday. The cotton net long was 3,266 contracts, after a net rise of 11,050 contracts on the week. The move to bet on higher prices coincided with a run-up in prices. The benchmark May contract on ICE Futures U.S. to 7 percent to