The governments of Iraq and its semiautonomous region of Kurdistan reached an interim accord to ease long-standing tensions over Kurdish oil exports, both sides said on Thursday. The deal marks a breakthrough after years of mutual hostility and is a step toward resolving one of the most vexing issues facing Iraqi national unity and the government’s ability to forge a united front against Islamic State jihadists in the country. Baghdad has alleged that the Kurdistan Regional Government’s efforts to develop and market its substantial oil resources independently of the federal government are unconstitutional and has fought them with diplomatic pressure, legal action and by suspending budget payments to the region.