Iran’s Kharg Island, home to a terminal through which the country exports most of its oil, has emerged as a focus of the war launched in late February by the United States and Israel.

Strikes on oil infrastructure on Kharg — or a ground invasion — would severely curb Iran’s oil exports, a key source of revenue for the Islamic Republic. An assault would also mark a major escalation that could provoke even heavier retaliatory attacks on Gulf Arab infrastructure and further drive up oil prices. The skyrocketing cost of fuel is already threatening the world economy.

U.S. President Donald Trump said strikes in mid-March “obliterated” Kharg’s military assets but did not target the island’s oil infrastructure. He warned that if Iran continued disrupting traffic through the Strait of Hormuz, he would reconsider the decision to spare energy targets on the island.

Then on Thursday, Trump said in a social media post that the U.S. would “assume total control” of Iran’s oil and gas industries, including the Kharg Island terminal, in the “not too distant future.”

The president made the post as escalating attacks between the countries pushed the Middle East closer to the resumption of a full-scale war. His latest threats emerged at a time when efforts to negotiate an end to the war appear to be stuck.

The island is on the other side of the Persian Gulf from U.S. bases in Kuwait and Saudi Arabia. A U.S. occupation of it would put American troops in a stationary position just 33 kilometers (21 miles) off Iran’s coast. That’s well within range of Iranian drones and missiles, if the Islamic Republic is willing to inflict damage on its own territory.

The small coral island is especially important because Iran’s coastline is mostly too shallow for tanker ships to dock. The U.S. has imposed a naval blockade on Iranian ports, which has impeded Iran’s efforts to export oil, mainly to China, through the Strait of Hormuz, even as Iranian attacks have closed the vital waterway to most traffic.

The destruction or loss of the island would deny the government a major revenue source, but it would also remove even more oil from world markets at a time of soaring prices. The destruction of the terminal would further damage Iran’s already weakened economy and undermine any efforts at postwar reconstruction.

Iran has continued to exert control over the strait, through which a fifth of the world’s traded oil passed before the war. Meanwhile, the U.S. has sent thousands of soldiers and Marines to the region.

Kharg Island has storage tanks and housing for thousands of workers. Gazelles roam freely near the refineries and depots. It also is home to a medieval Portuguese fortress and the ruins of one of the oldest Christian monasteries in the Persian Gulf.