The threat of mines being laid in the Strait of Hormuz poses a huge challenge for any ships contemplating passing through the vital waterway, a military expert tells CNN.

Sources have told CNN that Iran has begun laying mines in the Strait of Hormuz, through which around 20% of the world’s crude oil passes.

Iran’s Islamic Revolutionary Guard Corps has previously warned that any ship passing through the strait would be attacked, and the channel has effectively been closed since the start of the war.

Retired US Maj-Gen. Mark MacCarley pointed to how narrow the strait is, just 20 to 24 miles apart at its narrowest point, and how placing mines in its waters could cause chaos for shipping.

“Those ships must avoid the mines, and the mines themselves, the placement of the mines, create a challenge for the ship operators,” he told CNN’s Elex Michaelson.

The threats of explosives would “funnel those ships into a very small vector,” he said.

If any ship was hit, the effect could be potentially magnified, the retired general explained.

“There is potential for impact between those… oil tankers and the mines… and the significant potential for blockage of parts of the Straits of Hormuz, if two or three of those huge tankers are in fact taken out,” he said.

That would “significantly would impact the economies of most of the world,” MacCarley said.