April 15 (UPI) — The U.S. military’s maritime blockade of Iran has “completely halted” sea-based trade with the Middle Eastern country, U.S. Central Command said late Tuesday.

President Donald Trump announced the blockade on Sunday after negotiations to end the U.S.-Israeli war with Iran collapsed.

The blockade of 12 U.S. warships, more than 100 fighter and surveillance aircraft and more than 10,000 soldiers began at 10 a.m. EDT Monday, an effort to prohibit maritime traffic to and from all Iranian ports.

According to U.S. military officials, it covers the entire southern coastline of Iran, including ports on the Arabian Gulf and Gulf of Oman, between which lies the Strait of Hormuz.

“A blockade of Iranian ports has been fully implemented as U.S. forces maintain maritime superiority in the Middle East,” Adm. Brad Cooper, Central Command commander, said in a statement.

“In less than 36 hours since the blockade was implemented, U.S. forces have completely halted economic trade going into and out of Iran by sea.”

Central Command said earlier Tuesday that no ships had made it through during the blockade’s first 24 hours and that six vessels had complied with U.S. forces’ direction to return to an Iranian port on the Gulf of Oman.

“The blockade is being enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas,” Central Command said.

The blockade comes amid a two-week cease-fire between the United States and Iran that Trump announced on April 8. During the fragile truce negotiations on a permanent end to the war were to be conducted.

However, negotiations with Iran collapsed in Pakistan on Sunday, seemingly over disagreements on Iran’s nuclear program and control of the Strait of Hormuz.

Not long after the war began with the United States and Israel attacking Iran on Feb. 28, Iran sharply restricted vessel traffic to the Strait of Hormuz, an important trade route through which flows roughly 27% of the world’s maritime trade in crude oil and petroleum products as well as 20% of global liquefied natural gas trade, according to the U.S. Congressional Research Service.

Iran’s control of trade through the strait has caused gas prices to spike, threatening countries with energy crises.

The U.S. blockade appears aimed at financially squeezing Iran by cutting it off from maritime trade revenue.

According to Maid Maleki, senior fellow of the Foundation for Defense of Democracies, a nonpartisan Washington, D.C., research institute, the blockade could cost Iran about $435 million a day.

“The blockade makes continued resistance economically impossible,” he said in a statement.