Dennis Ross, a former special assistant to President Barack Obama, is the counselor and William Davidson distinguished fellow at the Washington Institute. Dana Stroul is a senior fellow at the Washington Institute and previously a senior staff member on the Senate Foreign Relations Committee covering the Middle East.

The Trump administration says its maximum-pressure campaign on Iran is working. If only that were true.

The administration has consistently made the argument that economic sanctions would deprive the Iranian regime of money and that less money would mean less bad behavior and more concessions at the negotiating table.

Bargaining with Iran is not the same as a closing a real estate deal, however, and Iran-sponsored terrorism is not easily reduced to counting dollars and cents. Less of one does not necessarily correlate to less of the other.

The inescapable conclusion, after surveying the region’s conflicts, is that a U.S. strategy based exclusively on starving Tehran of money cannot by itself compel changes in Iran’s regional behavior.

In Syria, Iran-backed Shiite militia groups may be suffering from salary cuts, but less take-home pay has not led to a reduction in violence, a reversal in battlefield gains by the regime of Bashar al-Assad, or a willingness by these foreign groups or Iranian forces to leave Syria. Militia fighters willing to travel to Syria from Afghanistan, Pakistan or Iraq will continue to answer Tehran’s call because of ideology or the abysmal economic conditions in their own countries.

Despite an announcement in March by Lebanese Hezbollah leader Hasan Nasrallah, which called for donations from supporters to replace revenue lost to sanctions, Hezbollah has not called home its fighters from Syria. Nor has the group diverted funding from its missile arsenal threatening Israel in southern Lebanon or from digging terror tunnels. Israeli strikes in Lebanon over the weekend targeting the fabrication of missile components reinforce the point that economic pressure alone is not preventing Tehran from trying to put precision targeting capabilities on tens of thousands of Hezbollah rockets.

In Yemen, Iran-supported Houthi fighters are intensifying the pace and sophistication of attacks against Saudi Arabia. Houthi ballistic-missile and drone attacks against civilian airports, oil pipelines and pumping stations in Saudi Arabia continue, with attacks now even in the eastern part of the kingdom. The evidence suggests that Iran is transforming its relationship with the Houthis from one of limited support in a local dispute to a regional partnership.

Sanctions pressure does not always equate to less Iranian cash for terrorism. In Gaza, Iran is reportedly increasing funding to Hamas from $70 million each year to $30 million each month, which is separate from the money it is giving Islamic Jihad.

Testifying to Congress in June, Brian Hook, the U.S. special representative for Iran, argued that U.S. sanctions have led to cuts in Iran’s military budget in 2018 and again in 2019. But these purported budget reductions did not translate into reduced threats in the Strait of Hormuz earlier this year, when Iran attacked with mines, attempted to seize commercial vessels and shot down a U.S. drone. The Pentagon is not counting on the maximum-pressure campaign to reduce Iran’s military aggression; this month, it issued a year-long warning of Iranian “aggressive actions” in the gulf region.

Hook also noted that the Iranian Revolutionary Guard Corps’ cyber command is low on cash. Yet a pair of cybersecurity firms pointed to Iran this year as the nexus in a wave of cyberattacks targeting government, telecommunications and Internet infrastructure entities.

Taken together, the fact pattern does not back up the Trump line that the maximum-pressure campaign is working. Well before the 2015 nuclear deal, Tehran had adopted a low-cost, asymmetric strategy because it cannot compete with the large defense budgets and conventional military capabilities of the United States, or of regional rivals such as Saudi Arabia and the United Arab Emirates. Sanctions alone will not be effective when Iran intentionally executes its regional terrorism campaign on the cheap.

A successful strategy toward Iran must be based on more than U.S.-imposed sanctions. Political isolation is also necessary, along with the credible threat of military force and readiness to offer Iran a way out of the economic pain and way in from the political cold.

Unfortunately, President Trump has been far better at isolating the United States than he has Iran. His administration has signaled in both statements and actions its unwillingness to use military force except in the narrowest of circumstances, creating a rift between the United States and its partners in the gulf region. Maximum pressure alienated European allies who have been integral to every other successful pressure approach imposed against Iran.

Taken together, these strategic missteps have emboldened Iran’s leaders. They clearly don’t feel the need to talk to the administration, having turned down a meeting at the White House for their foreign minister and conditioning any talks on the administration lifting sanctions. And their attempt to use drones to carry out a terrorist attack against Israel shows their willingness to take risks.

History tells us that Iran will not be sanctioned into changing its behavior. A successful policy of leverage comes from collective international pressure, the prospect that negotiations can offer credible economic gains and the threat of meaningful consequences for malign actions.

Read more:

The Post’s View: The hype over possible U.S.-Iran talks obscured something much more ominous

Jason Rezaian: Trump must stop sanctioning Iranians to death

Max Boot: Trump’s ‘coalition of one’ can’t beat Iran and China

Jason Rezaian: Journalism in Iran nears extinction