Chief executives of major US oil companies delivered a grim warning to officials in President Donald Trump’s administration during a series of meetings at the White House, saying the energy crisis sparked by the war with Iran could worsen.

According to The Wall Street Journal, citing sources familiar with the discussions, the CEOs of Exxon Mobil, Chevron, and ConocoPhillips warned that disruptions to energy flows through the Strait of Hormuz could continue to create sharp volatility in global energy markets.

Exxon Mobil CEO Darren Woods told officials that oil prices could rise beyond current elevated levels if speculative trading pushes prices unexpectedly higher, and that markets could face shortages of refined petroleum products.

Meanwhile, Chevron CEO Mike Wirth and ConocoPhillips CEO Ryan Lance expressed concern about the scale of the disruption.

President Trump did not attend Wednesday’s meetings. US oil prices rose from $87 per barrel that day to about $99 per barrel by Friday.