With low spare capacity, OPEC may not cope with return of Iranian sanctions

Curbs on Iran's exports through the re-imposition of sanctions may tighten the market too much even for Saudi Arabia to ignore

After more than a year of assessing how effective OPEC and friends have been at keeping a lid on supply, it's fair to ask how much more they can produce. This is really a question about spare production capacity -- and it's an urgent one.

President Donald Trump has to decide by May 12 whether to extend waivers on Iranian sanctions, and all the indications are that he won't. The drop in supply could easily exceed a million barrels a day, if the president decides to impose extra-territorial sanctions on anyone doing business with Iran -- would-be buyers could decide