US President Donald Trump issued an ultimatum, threatening to “massively blow up” the South Pars gas field—the largest in Iran—unless Tehran immediately halts its strikes on Qatari energy infrastructure.

The warning follows a series of Iranian missile attacks that caused extensive damage to Qatar’s Ras Laffan LNG facility.

Tehran has carried out a series of attacks on Gulf energy sites, including on Qatar’s huge Ras Laffan LNG facility, in retaliation for an Israeli strike on Iran’s South Pars gas field — part of the world’s largest natural gas reservoir.

While Trump maintained that the U.S. was not involved in previous Israeli strikes on Iranian assets, he vowed that “no more attacks” would be made by Israel if Iran complies, while simultaneously promising a devastating American military response if the aggression continues.

Tensions in the region have already brought tanker traffic through the Strait of Hormuz to a near-standstill, threatening a fifth of the global oil trade.