As he seeks a second term, US President Donald Trump is accelerating his favorite foreign-policy tool of economic sanctions but his "maximum pressure" campaigns have produced few of the results he has been seeking.

The Trump administration on Thursday imposed sweeping sanctions on Iran's banks, hoping for a knock-out blow to the adversary's economy, and in recent weeks has issued nearly daily actions against players in countries that include Belarus, Cuba, Nicaragua, Syria and Venezuela.

"Sanctions have clearly been the tool of choice for the Trump administration to respond to rogue regimes and illicit conduct," said Richard Goldberg of the Foundation for the Defense of Democracies, a hawkish group close to the Trump administration.

President Donald Trump, speaking in September 2020 in Jacksonville, Florida, has ramped up the use of economic sanctions
President Donald Trump, speaking in September 2020 in Jacksonville, Florida, has ramped up the use of economic sanctions AFP / Brendan Smialowski

"Past administrations commonly used sanctions but did so on a more narrow, targeted basis -- designating specific entities and individuals rather than attempting to create macroeconomic changes and destabilize governments to force wholesale behavioral change."

No country has been hit harder by US sanctions than Iran, with Trump in 2018 walking out of a denuclearization deal negotiated by former president Barack Obama and moving to block all oil exports from the clerical-run nation.

While denying the goal was regime change, Secretary of State Mike Pompeo set 12 conditions for the removal of sanctions that amounted to a full-fledged reversal of Iran's security strategy such as support of regional militants.

An Iranian woman checks a display board at a currency exchange shop in Tehran in September 2020 as US sanctions wreak havoc on the economy
An Iranian woman checks a display board at a currency exchange shop in Tehran in September 2020 as US sanctions wreak havoc on the economy AFP / ATTA KENARE

More than two years later, the Trump administration claims credit for devastation to Iran's economy, saying that its regional allies such as Hezbollah have been deprived of cash.

"In Iran, the regime has considerably less resources to spend on malign activities, which is itself a national security victory for the United States, and it appears the regime will be forced to negotiate in 2021 with whoever wins the presidential election," Goldberg said.

But Iranian-backed militant groups have been stepping up their activities, Iran has taken steps away from the restrictions imposed by the nuclear accord -- and none of Pompeo's 12 stated goals have been achieved.

Mourners carry the coffins of Iraqi paramilitary chief Abu Mahdi al-Muhandis, Iranian commander Qasem Soleimani and eight others inside the Shrine of Imam Hussein in the holy Iraqi city of Karbala in January 2020 after they were killed by a US strike
Mourners carry the coffins of Iraqi paramilitary chief Abu Mahdi al-Muhandis, Iranian commander Qasem Soleimani and eight others inside the Shrine of Imam Hussein in the holy Iraqi city of Karbala in January 2020 after they were killed by a US strike AFP / Mohammed SAWAF

"They would say 'we have weakened Iran' -- which is true -- but there hasn't been a real change in Iranian behavior," said Thomas Wright, a foreign policy expert at the Brookings Institution.

"We haven't seen Iran agree to a negotiation, let alone negotiate an alternative to the JCPOA," he said, referring to the Iran accord by its acronym.

Brian O'Toole, who helped implement sanctions under the Obama administration, said the latest sanctions on Iran were more about politics including making it more difficult for a future administration to re-enter the nuclear accord.

A worker of Venezuelan state oil company PDVSA watches the Iranian oil tanker Fortune dock at El Palito refinery
A worker of Venezuelan state oil company PDVSA watches the Iranian oil tanker Fortune dock at El Palito refinery AFP / -

"The real impact of these sanctions is likely to be marginal, and certainly not to the level of regime collapse as has reportedly been touted by some proponents," said O'Toole, now at the Atlantic Council.

"And it will do little to cut down on Iran's bad behavior," he said.

The Trump administration's goal has been explicit in Venezuela -- the removal of leftist leader Nicolas Maduro, whose re-election in 2018 was widely seen as fraudulent.

But after more than a year and a half of US efforts including sanctions on Venezuela's oil, Maduro remains in charge with support from Russia, China, Iran and Cuba.

The results are more complex on North Korea, which was hit by major UN-blessed sanctions after a series of nuclear and missile tests.

Experts see the economic pressure as one reason why North Korean leader Kim Jong Un embraced diplomacy with Trump, whom he met in a landmark 2018 summit and twice again last year.

The refusal by Trump, under pressure from his aides, to ease sanctions on North Korea without a final deal scuttled a 2019 summit with Kim in Hanoi.

Trump has taken credit for easing war-like tensions with North Korea but the authoritarian state has still been pursuing its nuclear development.

Goldberg saw a sanctions success story with Turkey which freed a detained US pastor after Trump's brief imposition of tariffs rocked the NATO ally's economy.

But Trump's enthusiasm for sanctions has tested relations with allies, with European nations struggling to preserve the Iranian nuclear accord.

European and other allies have voiced annoyance but reluctantly complied as the United States laid out secondary sanctions, threatening to punish any nation that does business with Iran.

"The US has been very interested in sanctions for a long time, but I think there is some recognition now in both parties this has to be part of a larger strategy and it can't be a strategy in itself, which is less effective," Wright said.

"I don't think Trump sees it that way, but I think there is a growing recognition of that."