The Trump administration is preparing a plan to ban exports of diesel for 90 days, despite splits inside the administration and with the oil industry, in a bid to bring down energy prices weighing on Republicans leading into the midterms, five people familiar with the discussions said Wednesday. A ban, the legal process of which is still being worked out, has been opposed by U.S. fuel producers who have warned that any short-term benefit would be outweighed by higher fuel prices in the future. Any halt to shipments would be the first restriction on U.S. energy exports since the Obama administration lifted a decades-old ban on oil exports in 2015.