U.S. President Donald Trump appears to be leading by example with his aggressive habit of imposing economic sanctions abroad when he's aggrieved, but his reliance on a blunt tool could set a dangerous geopolitical trend.

So say international trade lawyers and former diplomats, who point to what they view as an uptick in world leaders deploying tariffs and economic sanctions, ostensibly to hurt governments they feel have crossed them.

Trump's Twitter declaration on Friday that the U.S. would double steel and aluminum tariffs on Turkey, imposed due to the imprisonment of an American pastor, appears to be the latest example.

It's "fairly unprecedented" for a president to resort to sanctions in such a way, said former White House director of global engagement Brett Bruen.

U.S. President Donald Trump has an aggressive habit of imposing economic sanctions abroad when he's aggrieved, experts say. (Carlos Barria/Reuters)

He believes this dependence on economic leverage for diplomatic coercion is unsustainable.

The detention in Turkey of Andrew Brunson, an American accused of espionage, should "without question be an issue raised between the leaders," Bruen said. Though he said this should be done through normal diplomatic negotiations, not a "rush to stage zero" that could cause collateral damage or lead to harmful reciprocity.

"Let's take the reverse case. What happens when we detain a Turkish or Chinese national — on grounds we believe are legal — and now they've seen the aggressive action the U.S. took?" said Bruen, who served during the Obama administration. "We're now in the Wild West of diplomacy. It's a shoot first, negotiate later world order. The precedent this sets is a dangerous one."

Although the U.S. applying financial punishments for political motives isn't a new tactic, "Trump has set the example for weaponizing" financial sanctions, said Gary Hufbauer, a senior fellow with the Peterson Institute for International Economics in Washington.

I have just authorized a doubling of Tariffs on Steel and Aluminum with respect to Turkey as their currency, the Turkish Lira, slides rapidly downward against our very strong Dollar! Aluminum will now be 20% and Steel 50%. Our relations with Turkey are not good at this time! —@realDonaldTrump

"We're kind of seeing a return to the law of the jungle, and it's kind of like gangbusters in terms of the use of this policy tool."

Sanctions seem to be de rigueur in the Trump era. Aside from recent metal tariffs on Canada, Mexico and European nations, this administration has applied sanctions to at least 11 countries, including: Iran, Turkey, Russia, China, North Korea, Pakistan, Syria, Venezuela, Cuba, Libya and Colombia.

That Trump has wielded this instrument so often in his first 18 months is already "inspiring imitators," said Gary Horlick, a leading Washington trade lawyer.

"I hate to use this term, but Trump has 'normalized' the idea. And once you start down that road, it's irresistible."

He gave the example of Saudi Arabia's ongoing feud with Canada, sparked by what might ordinarily be viewed as a routine critique from the Canadian foreign affairs minister about the Kingdom's human rights record.

Riyadh hit back last week by suspending Saudi airline flights to Canada, freezing bilateral trade and investment, and withdrawing its high-tuition-paying Saudi university students.

Saudi Arabia might never have considered responding this way to Canada "10 years ago," he said, adding that the ultimate fear is that tit-for-tat sanctions lead to a "downward spiral" in diplomacy.

Andrew Craig Brunson, an evangelical pastor from Black Mountain, N.C., faces espionage charges that could lead to a lengthy prison sentence in Turkey, where he has lived for several years. (Emre Tazegul/Associated Press)

If the president continues at this rate, staff burnout in U.S. sanctions agencies is another concern, according to an essay in Foreign Policy by a former senior adviser at the Treasury Department and a former State Department official.

Former Treasury Department official Hal Eren generally supports Trump's rationale for metal tariffs on partners like Canada on national security grounds. But he doubts that Riyadh would have been so quick to pull the trigger on hitting Canada with economic punishments had it not been for Trump making sanctions "the foreign policy instrument of choice these days."

"It's on their radar screen. It's probably why it occurred to them," said Eren, a former senior sanctions adviser for the Treasury.

"Everyone's getting into the act, like if the U.S. can do it, we can do it as well."

Warren Maruyama, a former U.S. trade representative counsel who served during the George W. Bush administration, isn't so sure.

The use of sanctions for diplomatic coercion has waxed and waned through presidential cycles, he said, though he added he's never seen an administration "more enthusiastic about tariffs" as this one.

It's 'fairly unprecedented' for a president to resort to sanctions the way Donald Trump does, says former White House director of global engagement Brett Bruen. (CBC)

When China wanted American airline carriers to stop referring to Taiwan as an independent island, Beijing in April threatened to disrupt lucrative U.S. travel to the rapidly growing market.

For the past year, Saudi Arabia, along with three other countries (Bahrain, Egypt and the United Arab Emirates), have enforced a trade embargo on Qatar over allegations it supports terrorism.

Trump's toughening of sanctions on North Korea were arguably effective for bringing North Korean ruler Kim Jong-un to the table at a summit with Trump in June. But recent satellite imagery has shown evidence that Pyongyang may not have been as serious about denuclearization as the U.S. had hoped.

Tariffs experts told CBC News that retaliatory measures, such as those aimed at the U.S. over its metals tariffs, are understandable, as are United Nations-mandated sanctions for violations of international laws such as the use of chemical or biological weapons on civilians. The UN pressed for sanctions against South Africa during apartheid, for example.

Trump, left, talks to Turkish President Recep Tayyip Erdogan, right at NATO headquarters in Brussels, Belgium, on July 11. Despite meeting several times, including last year at the White House, the leaders have not settled a number of issues of disagreement. (Presidency Press Service via AP)

But Bruen, the Obama adviser, noted that in the case of Brunson's imprisonment in Turkey, "the strategic interests we have are often greater than the issue of one American or several Americans' detentions."

Turkey, for instance, is an ally in the North Atlantic Treaty Organization and sits in a strategically important region near Syria, Iran and Iraq.

"We need to zoom out from the just concern for this American's well-being and ensure that we can compartmentalize that issue."

Trump's clashes with allies in NATO and the G7, as well as the withdrawal from the Paris climate pact and the Iran nuclear deal, threaten to deepen rifts when there may be need for co-operation on sanctions with U.S. allies.

The escalation of sanctions on Turkey in the Brunson case shouldn't become a model, he said.

"If the expectation is that every time an American is detained overseas, either justly or unjustly, the U.S. is going to need to impose sanctions to secure their release," he said, "we're going to end up in situation where we've got sanctions against a whole host of countries."