Washington (CNN) Imposing sanctions has become the Trump administration's go-to move to signal to the country and the world that it's doing something about a problem.

After President Donald Trump said he had called off a military strike on Iran shortly before it was to begin, he followed up by imposing new sanctions. This comes on top of the Obama-era sanctions he reimposed on Iran after pulling out of the Iran nuclear agreement.

Iran's ambassador to the UN described the US actions as "economic war and terrorism against the Iranian people."

The sanctions are barely felt in the US, but their effect on Iran -- barring US companies from doing business there and prohibiting access to the USbanking system -- has contributed to a crippling economic situation

They're also a tool Trump has access to without the OK of Congress or that Congress can force upon him, as it did with regard to Russians indicted by special counsel Robert Mueller for election interference.

So how effective is this device that's short of military action but more than simple diplomacy?

Their use is rising

Sanctions have been used increasingly by presidents of both parties since September 11, 2001, after which the government used them to target supporters of terrorism, according to John E. Smith, a former director of Treasury Department's Office of Foreign Assets Control, which manages US sanctions, who is now a partner at the law firm Morrison and Foerster.

He said a good way to think about them is as "the alternative between words and war, between mere diplomacy and boots on the ground."

But the Trump administration, he said, has accelerated the use of sanctions further, due to Trump's embrace of confrontation.

"I think the administration is more willing to confront traditional allies and partners, as well as those countries that it is engaged in diplomatic, military or political standoffs with," said Smith, pointing out that the Iran sanctions were reimposed over the objections of European allies. He also noted that the administration has targeted officials in Turkey, a NATO ally of the US, with sanctions.

Sometimes they work, sometimes they don't

The Obama administration used sanctions in conjunction with allies and others to pressure Iran. The Trump administration has upped the sanctions on Iran unilaterally and is in turn threatening European allies, Japan and India with US sanctions if they don't go along.

Trump seems to be using the sanctions both to punish Iran for downing a US drone and to force Tehran to the negotiating table, but Iranians have said they will close the diplomatic channels

The Cuba sanctions , which the US has imposed unilaterally and which virtually no other country has agreed with, have been in place for decades and have not been credited with making a change in the government of Cuba's calculations," Smith said.

"The resumption of sanctions on Iran by the US alone -- without the Europeans, the Asians, other members of the UN Security Council -- may be saddled with that same difficulty in achieving change, given that the rest of the world largely disagrees with the objectives and the mechanisms the US has employed," he said.

But when sanctions levied against Iran by the Obama administration were imposed as part of a coalition of European, Asian and North American countries, they got Iran to the negotiating table, he said.

They're imposed for all kinds of reasons

The Treasury Department maintains a massive list of " Specially Designated Nationals and Blocked Persons " subject to sanction. It's got thousands of names. The data firm Enigma has analyzed the list and found names around the world. While Smith said the list is updated regularly, some people are never removed. For instance, Slobodan Milosevic, the Yugoslav war criminal, is still listed. He died in 2006.

Most sanctions have been levied for narcotics trafficking and terrorism, according to the Enigma analysis.

to the diamond trade to the global war on terror. The Treasury Department currently lists 30 separate sanctions authorities that range from action against transnational criminal organizations like the Yakuza crime gangsto the diamond trade to the global war on terror.

But sanctions are most commonly associated with countries, like Iran, or, another country the Trump administration has reimposed action against, Cuba. The government recently settled with Expedia for helping more than 2,000 people buy travel to Cuba through foreign subsidiaries owned by the Seattle-based travel site.

And from that perspective, sanctions may be of limited utility. The US has been targeting Cuba, North Korea and Iran for decades, but all three regimes remain.

It can be difficult to keep up with US sanctions. For instance, Russia, Russian companies and Russian nationals are the target of US sanctions for a variety of reasons, according to a Congressional Research Service report outlining the entire universe of Russia-related actions.

These include:

The invasion of parts of Ukraine by Russia in 2014

The cyberattack on the 2016 US presidential election

Human rights abuses

Use of a chemical weapon on a former Russian spy and his daughter in the UK

Facilitating trade with North Korea

Russian banks involved in Syria

Selling weapons to Iran, North Korea and Syria

Individuals facing sanctions with respect to terrorism and international crime

Sanctions against Iran are similarly scattered , which also can muddy their effect.

'Functioning under an illusion'

"Sanctions are increasingly being used as a political tool to demonstrate that 'something' is being done without real regard to their effectiveness, which threatens to devalue their currency over time," Michael Carpenter, director of the Penn Biden Center for Diplomacy and Global Engagement, told lawmakers in May.

In fact, sanctions alone likely won't accomplish much, said Elizabeth Rosenberg of the Center for a New American Security, who's a former senior adviser at the Treasury Department.

"They may help to create economic leverage, which when coupled with other instruments of policy -- military force protection, diplomacy, covert action, multilateral efforts of collaboration -- in fact they can be meaningful to help accelerate a process of diplomatic negotiation or a stability operation," according to Rosenberg.

"But if we think that sanctions will cause regime change, then we are wrong."

Politicians and policy makers are not likely to stop using them, however, since they give the appearance of action.

"People are functioning under an illusion where they believe this is a muscular tool that can get it done when words don't do enough and military action isn't available," said Rosenberg.