With the announcement of an agreement to extend a ceasefire and reopen the Strait of Hormuz, Friday is the day President Trump said merchant ships can once again sail unimpeded through the Strait, or as he pronounced, "Ships of the world, start your engines."

Well, not so fast.

Despite the president's pronouncement, there are still questions about how quickly commercial ships can start moving, and whether Iran will truly allow those ships to resume free access in what is an international waterway. There are still some 1,500 ships stuck inside the Persian Gulf waiting to leave, according to industry analysts, including hundreds of ocean-going vessels such as oil tankers.

Before the U.S. and Israel waged war against Iran at the end of February, 140 ships passed through the Strait each day, according to both industry analysts and U.S. officials. The attacks against Iran led its leaders to close the Strait to traffic by firing drones and missiles at ships and laying mines along the shipping lanes, according to U.S. officials.

The U.S. has already started removing some of those mines and opened up a new pathway off Oman so ships can leave and not have to hug the Iranian coast, said Capt. Tim Hawkins, spokesman for U.S. Central Command.

"It's been a U.S. effort," Hawkins said, adding he would not talk about how long such an effort would take.

But now that an agreement has been announced, Britain and France will take part in demining, Prime Minister Keir Starmer said this week.

"The UK and France have taken a leading role up to this point," he said, "particularly to offer support on mine clearance in an agreed way."

British officials said they would deploy autonomous mine hunting sea drones along with counter drone systems, Typhoon jets and the HMS Dragon, all part of a defensive mission to secure freedom of navigation. American officials have not detailed what assets the U.S. military is using for the demining mission, but military analysts say the U.S. is using a mix of drone boats, helicopters and warships.

A U.S. official briefing reporters this week said an increased number of commercial ships are already transiting that southern route off Oman.

"We've been getting as much as 25 ships through a day," said the official, who asked not to be identified under the ground rules for the briefing. "I think they'll probably go to maybe 40 to 50 pretty quickly. That's just the southern line. By Friday, everything will be fully open."

As far as when there will be business as usual for the Strait of Hormuz? "So I think it will return to normal pretty quickly, definitely within 30 days," the official said.

"That's realistic based on the fact that the U.S. has taken out a high number of [Iran's] minelaying vessels," said Scott Savitz, a senior engineer at the RAND School of Public Policy who has provided analytical support to the U.S. Navy and its mine warfare command. And the demining efforts should achieve "an acceptable level of risk," he added.

Still, Tom Bartošák-Harlow, a spokesman for the International Chamber of Shipping, a trade association for shipowners and operators, doubted whether merchant ships would quickly start their engines and head for the exit.

"There's still a lot of risks associated with transit," he told NPR in an email. "It's very likely to be a gradual process of confidence amongst shipping companies. That's likely to be through a series of actions rather than just one."

He cited two of those actions: "Confirmation" that the areas of transit do not contain mines, as well as assurances that the agreement between the U.S. and Iran "is holding."

Besides de-mining, there's also the issue of any kind of fees imposed by Iran on commercial ships sailing through the Strait of Hormuz.

Bartošák-Harlow said there's no conclusive evidence of who has and who has not paid a toll in the past, and there wasn't any sort of record, adding that companies should not be paying a toll for passage through an international waterway.

Trump insisted the Strait of Hormuz will be "permanently toll free" and Vice President JD Vance said it will be "toll free for the long term." The Iranian Revolutionary Guard Corps set up a so-called toll booth back in March. It's unclear whether any ship owners paid the toll.

Now, a spokesman for Iran's Foreign Ministry, Esmaeil Baqaei, says vessels transiting the Strait will not pay tolls but instead pay "service fees" for navigation-related facilities, environmental protection and maritime support services.

That distinction does not pass legal muster, said James R. Holmes, chair of maritime strategy at the U.S. Naval War College.

"There is no provision in international law for a coastal state charging for passage through a natural waterway, whether you call it a toll or a fee or whatever," Holmes told The New York Times.

What's uncertain is whether the Trump administration, once the agreement is unveiled, will agree that a toll and a fee are one and the same.