Saudi Arabia and Russia, the architects of an oil production cut that has stabilized prices, presented a united front on compliance just as rising U.S. inventories have sparked doubts about the OPEC and non-OPEC deal. Khalid Al-Falih, the Saudi energy minister, acknowledged that global crude inventories aren’t draining as quickly as he expected, opening the door for an extension of the production cuts into the second half of the year. The potential rollover is a subtle yet significant shift from just six weeks ago, when the minister said that an extension probably wouldn’t be needed. Al-Falih’s concern about the slow pace of stockpile reductions was echoed by Suhail Al-Mazrouei, the oil minister for the United Arab Emirates. Since the Organization of Petroleum Exporting Countries and some of its rivals, including Russia, agreed to cut output in late 2016, oil prices have stabilized at around $50-$55 a barrel, up from $45-$50 a barrel before. Yet, prices are struggling to rise further as U.S. crude stocks increased to record levels. With the market starting to believe the cuts were backfiring by reviving U.S. oil production, Al-Falih and his Russian counterpart Alexander Novak called a news conference in Houston after a round of meetings to offer a united front, and insist the cuts will work.