President Donald Trump may soon need to choose between two recurring fixations: battling OPEC nations, and cheap oil.

After announcing sanctions on Venezuela’s state-run oil company PDVSA this week, the president is now in conflict with two of the cartel’s founding members, having imposed similar measures against Iran late last year. Trump is pressuring the Islamic Republic over its nuclear program, and squeezing Venezuela’s President Nicolas Maduro for fraudulently clinging to power.

Iranian shipments have already slumped by 1.3 million barrels a day, and about 500,000 barrels a day of Venezuelan crude which has been banned by the U.S. will soon need to find new buyers. The overall disruption could be much bigger if America succeeds in choking off Iran’s exports entirely, or if sanctions on Venezuelan oil are applied more broadly, as suggested in a tweet from National Security Adviser John Bolton.

However, knocking out oil-supplies from the petro-states is likely to conflict with another of the U.S. president’s goals: lowering gasoline prices to appease motorists and stimulate the American economy.

Though prices remain at about $54 a barrel in New York, 30 percent below the four-year peak reached last October on concern that Trump may not grant waivers for buyers of Iranian crude, that calm might not last, and the U.S. may need to decide between the two aspirations.

In May, Trump will decide whether to renew temporary exemptions that allowed eight of Iran’s customers -- including China and India -- to continue buying reduced quantities from the Islamic Republic. If these waivers aren’t extended, Iranian shipments will likely slump further.

To fill the gap, Treasury Secretary Steve Mnuchin has said America’s Middle East allies, Saudi Arabia in particular, are ready to restore production. The kingdom ramped up output to record levels last autumn when it seemed Trump was serious about shutting Iran’s trade down completely.

The question is whether the Saudis and their allies can increase production high enough, and keep it there, to compensate for simultaneous losses in Iran and Venezuela. Although the kingdom sits on about 1.4 million barrels a day of spare production capacity, according to the International Energy Agency, even that could be strained by a deep and prolonged outage.

“A word of warning: the US cannot simultaneously choke off supplies in both Venezuela and Iran without causing a spike in prices,” said Stephen Brennock, an analyst at PVM Oil Associates Ltd. in London.