WASHINGTON (AP) — President Donald Trump has turned to naval blockades to pressure the governments of Venezuela, Cuba and now Iran to meet his demands, but his preferred tactic is confronting a very different reality in the Middle East than in the Caribbean.

Unlike Cuba or Venezuela, Iran choked off a crucial trade route for energy shipments, meaning the longer the standoff persists the more the global economy will suffer. Tehran also poses a greater military threat — beyond those posed by the adversaries in America’s own hemisphere — and requires a sustained military presence far from U.S. shores.

Iran’s leverage over the Strait of Hormuz gives it power during a shaky ceasefire because the widening economic risks — especially higher U.S. gas prices in an election year — could force Trump’s Republican administration to end its blockade on Iran’s ports and coastline, experts say.

“It’s really a question now of which country, the U.S. or Iran, has a greater pain tolerance,” said Max Boot, a military historian and senior fellow for national security studies at the Council on Foreign Relations.

Iran presents ‘major differences’ from other blockades
The effectiveness of Trump’s pressure tactic — using the world’s most powerful navy to block the trade of Iran’s sanctioned oil and other goods — is still very much up for debate. Some experts say Trump’s success in Venezuela likely had more to do with the U.S. military raid that captured leader Nicolás Maduro than American warships seizing sanctioned oil tankers to enforce U.S. control over the South American country.

A U.S. oil embargo on Cuba, meanwhile, has caused the island’s most severe economic crisis in decades. While U.S. and Cuban officials have met recently on the island for rare talks, the financial strangulation has failed to produce the Trump administration’s stated goal of leadership change.

“I do think that the success of the Maduro mission in Venezuela has probably emboldened the president,” said Todd Huntley, director of Georgetown University’s National Security Law Program.

That doesn’t make the situations in Venezuela and Iran similar — geographically, militarily or politically. “There are some major differences,” said Huntley, a retired Navy captain and judge advocate general.

While the blockade against Iran has delivered a severe blow to its economy, including stopping freighters from importing various supplies, the country has still been able to move some of its sanctioned oil, ship tracking companies say.

And Iran has rejected Trump’s demands to reopen the Strait of Hormuz, where 20% of the world’s oil normally flows, and it has been firing on ships again this week. Stalled shipments through the strait have sent gasoline prices skyrocketing far beyond the region and raised the cost of food and a wide array of other products, creating a political problem for Trump ahead of the midterm elections in November.

“Blockades are usually just one tool of a mechanism used in a conflict,” said Salvatore Mercogliano, a maritime history professor at Campbell University in North Carolina. “They can be important. But it’s only one element. And I don’t think it’s going to be enough to convince the Iranians.”

The effectiveness of the US blockade has been called into question
Adm. Brad Cooper, head of U.S. Central Command, claimed last week that “no ship has evaded U.S. forces.” The command overseeing the Middle East said it has directed 31 ships to turn around or return to port as of Wednesday.

Merchant shipping groups are skeptical. Lloyd’s List Intelligence said “a steady flow of shadow fleet traffic” has passed in and out of the Gulf, including 11 tankers with Iranian cargo that have left the Gulf of Oman outside the strait since April 13.

The maritime intelligence firm Windward said this week that Iranian traffic continues to flow “via deception.”

Iranian ships have several ways to sneak through the blockade, including spoofing their location tracking data or traveling through Pakistani territorial waters, Mercogliano said. He also noted that the sheer volume of shipping traffic the military needs to screen is a challenging task.

Blockades require patience to work
The last time the U.S. mounted a blockade similar to the one focused on Iranian ships was during the Kennedy administration in the early 1960s, when the U.S. imposed a blockade on Cuba, Huntley said.

“And it wasn’t even called a blockade,” he said. “We called it quarantine.”

Some naval blockades over the course of history have had an impact, such as Britain’s blockade on Germany during World War I. “But they tend to be very long-term impacts, whereas Trump is looking for short-term, quick results,” according to Boot, the military historian.

He said Trump probably saw the blockade on sanctioned oil tankers tied to Venezuela as playing a large role in the success of leadership changes in that country. But Boot said it had more to do with the U.S. ousting Maduro and the subsequent cooperation from his vice president and now-acting president, Delcy Rodríguez.

“There is no Delcy Rodríguez in Cuba or Iran,” Boot said. “I think his success in Venezuela led him astray, thinking that this was a template that could be replicated elsewhere. He sees it as a huge success at little cost. And, in fact, it turns out to be a unique set of circumstances.”