A former U.S. diplomat thinks Iran is pushing President Donald Trump’s buttons to see how far he and his administration will go as tensions mount in the Middle East.

“Whether you’re talking about the tanker attacks or previous pipeline attacks or now this, they continue to raise the ante, they raise the bar, almost daring Donald Trump to respond.”

Gerald Feierstein, former U.S. Ambassador to Yemen, which borders Saudi Arabia, Oman and the Red and Arabian seas, argues Trump and his administration’s main objective is to find “ways to get the Iranians back to the negotiating table,” but Tehran has a different approach after Trump unilaterally pulled out of the 2015 Iran nuclear deal last year.

“Clearly, the Iranians look inclined to test the Trump administration, to call Donald Trump’s bluff, if you will, to see if he really has the will to really go all the way,” Feierstein said in an interview with CNBC Wednesday. “So far, their bets have paid off.”

A coordinated strike on Saudi Arabian oil facilities over the weekend is the latest in a string of events that have ratcheted up tensions in the region. Tehran denies involvement, but both the U.S. and Saudi Arabia allege otherwise.

Washington has also blamed the Islamic Republic for recent attacks targeting oil tankers in the Strait of Hormuz, a key waterway for the world’s oil supply, and for shooting down a U.S. military drone in the wake of the events involving the tankers.

“Whether you’re talking about the tanker attacks or previous pipeline attacks or now this, they continue to raise the ante, they raise the bar, almost daring Donald Trump to respond,” Feierstein said.

It’s a dangerous balancing act, though, as Trump doesn’t want to start another war in a region that has been ravaged by conflict. The Trump administration’s “maximum pressure” campaign against Iran is hammering its economy, but Feirstein still thinks it “would not want to do things that would take the opportunity or the possibility of a negotiation away completely.”

In his latest move, Trump tweeted Wednesday that he has asked Treasury Secretary Steven Mnuchin to “substantially increase” sanctions against Iran. Details of the increases were not available at the time of publication.

Trump and Iranian President Hassan Rouhani could potentially meet next week during the United Nations General Assembly in New York, but Rouhani has threatened to cancel Iran’s appearance if the U.S. doesn’t issue visas to his delegation soon, according to the Islamic Republic News agency.