The U.S. began mine-clearing efforts over the weekend. The commander of CENTCOM, Adm. Brad Cooper, said U.S. forces would begin the “process of establishing a new passage” that would be shared “with the maritime industry soon to encourage the free flow of commerce.”

Iran's own blockade of the strait not only sent energy prices up but also increased the price of fertilizer and threatened the economies of countries worldwide.

Tehran has repeatedly ignored Trump's demands that it reopen the waterway, and instead, it began charging some ships millions of dollars to transit Hormuz.

CENTCOM said it would reveal more information on its plans to commercial mariners through a formal notice before the blockade started Monday.

Iran’s Revolutionary Guard, meanwhile, warned that any military vessels attempting to approach Hormuz would be considered in violation of the ceasefire deal agreed to between Washington and Tehran and would receive a firm response.

Iran's armed forces said the blockade amounted to "piracy."

Risks and rewards

Enforcing the U.S. blockade will be a complicated, "high-risk" and legally contentious endeavor, said Andreas Krieg, a senior lecturer at King’s College London’s School of Security Studies.

"Practically, this would look less like a clean historical blockade and more like a messy, high-risk interdiction regime," he said.

The U.S., he said, would need to identify, track, hail, divert and maybe even board vessels linked to Iranian ports, all while “operating in one of the most crowded and politically sensitive waterways in the world.”

By early Monday, hours before the blockade was set to come into effect, ships appeared to be largely steering clear of the strait, with significantly fewer ships in the area compared to the day prior, real-time and historic vessel tracking provided by Kpler showed.

Outside of ships proactively avoiding the strait, Krieg said, enforcement would likely rely on a mix of naval patrols, surveillance, maritime warnings, allied intelligence and selective interdiction. He said that could even involve the boarding of ships, as was seen in Venezuela.

“Bandwidth” could become a real issue for the U.S., while mine-clearing efforts could put American ships at risk, he said.

CENTCOM has said it had begun “setting conditions for clearing mines” in the strait Saturday, with two U.S.-Navy guided missile destroyers deployed in the operations.

If the blockade is successful in cutting off Iran’s oil flows, it could have a crippling effect on the Islamic Republic, which is extremely reliant on its oil exports.

Countries like China, which imports nearly a third of its oil through the strait, could also be hit hard, with a prolonged conflict “actively affecting China’s domestic consumption,” including oil prices, said Zhu Feng, dean of the School of International Studies at China’s Nanjing University.

Guo Jiakun, spokesperson for the Chinese Foreign Affairs Ministry, on Monday urged the U.S. and Iran to "remain calm and exercise restraint," saying "the way forward is to achieve an early ceasefire and an end to hostilities."

Meanwhile, Mukesh Sahdev, chief oil analyst at XAnalysts, said, the U.S. should ultimately be able to withstand higher gas and oil prices better than Iran can weather a major blow to its export income. If successful, he said the blockade could prove to be a "master stroke" in the conflict with Iran.

Still, Washington's blockade could not only be a high-risk endeavor, but also a legally "contentious" one, Krieg said.

"A blockade is one of the most escalatory tools a state can use at sea, and its legality depends on context, proportionality, discrimination and the underlying state of armed conflict," he said.