President Donald Trump has spent months talking tough about Iran. Tehran’s surprise decision this weekend to sentence an American citizen to 10 years in prison on trumped-up spying charges means the president will now have to decide whether to actually act on those words.

Xiyue Wang, a graduate student studying history at Princeton University and an American citizen of Chinese descent, was doing research for his doctoral project in Iran when he vanished last summer, according to a statement from Princeton.

At a news conference in Tehran, Iranian judicial spokesperson Gholam Hossein Mohseni-Ejei said Wang “was gathering [information] and was involved in infiltration.”

While Mohseni-Ejei did not mention Wang by name, instead calling him one of “America’s infiltrators,” the Mizan news agency, the mouthpiece of Iran’s judiciary, provided his name and age, 37.

The so-called information that Wang was gathering were actually 100-year-old documents from Iran’s public archives about the administrative and cultural history of the late Qajar dynasty from 1794 to 1925, according to the Washington Post.

“We are aware of reports regarding Xiyue Wang, a US citizen detained in Iran,” said a US State Department official in an emailed statement. “We call for the immediate release of all US citizens unjustly detained in Iran so they can return to their families.”

White House Press Secretary Sean Spicer said that the White House is “keeping an eye on” Wang’s detainment. President Trump hasn’t yet spoken publicly on the incident, but experts speculate that he will push for increased pressure on Iran.

Trump talks tough about Iran. Will his deeds match his words?

Wang’s sentence comes at a time in which US-Iran relations have already “hit rock bottom,” according to Sanam Vakil, a professor of Middle East studies at the Johns Hopkins School of Advanced International Studies.

There are at least four American-Iranian dual citizens currently detained in Iran on unverified charges. Iran was included on the list of banned countries in Trump’s travel ban. The US is also strongly backing Saudi Arabia in an ongoing cold war between the two countries.

And Iran is one of Trump’s favorite targets, going back to his campaign when he constantly blasted the pact reached by President Obama to curb Iran’s nuclear program as the “worst deal ever.”

In a speech encouraging Arab countries to stop trading with Iran, Trump emphasized his hawkish position.

“Until the Iranian regime is willing to be a partner for peace, all nations of conscience must work together to isolate Iran, deny it funding for terrorism, and pray for the day when the Iranian people have the just and righteous government they deserve,” he said in Saudi Arabia in May.

And when Tehran was rocked by a deadly terrorist attack in June that killed 12 people, the White House issued a statement essentially blaming Iran for the attack on its own citizens: “We underscore that states that sponsor terrorism risk falling victim to the evil they promote.”

Wang’s sentence is yet another example Trump can use to justify his anti-Iran platform. At this point, we can only speculate on Trump’s response, but Vakil posed several options: “Condemnation, and perhaps increasing serious criticism of Iran’s human rights abuses, and maybe considering elevating this in some way in Congress.”

Trita Parsi, the author of a new book on US-Iran relations, Losing an Enemy: Obama, Iran, and the Triumph of Diplomacy, said that Trump was likely to respond by increasing pressure on Iran through imposing new sanctions and encouraging other Arab countries to stop trading with Iran, rather than relying on diplomacy.

“So far all we’ve seen from the Trump administration is a focus on pressure; there’s no focus on diplomacy,” he said.

The US Senate already voted in favor of new sanctions on Iran over its ballistic missile program and other activities not mentioned in the nuclear deal. To become law, the measure needs to be passed by the House of Representatives and signed by Trump. But it has yet to be brought to the floor for a vote.

But at the same time, the Trump administration said on Monday night that Iran is honoring the nuclear deal, only after Trump argued with top advisors for hours. Under the terms of the nuclear pact, the administration must certify every 90 days that Iran is complying with the terms of the deal.

So it’s ultimately unclear whether Wang’s sentence will push Trump to take more dramatic action on Iran.

Wang’s sentence says a lot about Iran’s internal politics

Wang’s arrest also illuminates the tense political situation within Iran over the future of US-Iran relations. Iranian hardliners oppose a more open relationship with the US, while other people in government, including President Hassan Rouhani, have pushed for increased openness, especially when it comes to economic ties.

Wang’s sentence comes on the same day that President Rouhani’s brother, Hossein Fereydoun, was detained in Tehran for unspecified financial crimes. Fereydoun was involved in the negotiations leading to the nuclear deal, putting him at odds with Iranian hardliners who oppose the pact and have long accused him of corruption.

The hardliners, many of whom come from the Islamic Revolutionary Guard Corps, effectively control Iran’s judiciary, conduct most intelligence investigations, and ultimately convict and sentence individuals they view as criminals. This all happens without input from the president, whose powers are constrained by Iran’s theocratic form of government.

The arrests of both Wang and President Rouhani’s brother reveal two aspects of the current Iranian political climate: First, it shows that President Rouhani doesn’t have the ability to push back against the hardliners within Iran who are undermining his authority, according to Vakil. And second, it demonstrates how hardliners wield power over Iran’s economy.

“Part of the reason why they’re doing this is because they understand that arresting the US citizens and Westerners, particularly on ridiculous charges like this, has a deterring effect against companies that have been thinking about investing in the Iranian economy,” said Parsi.

According to Parsi, Iran’s hardliners oppose foreign economic investment because they fear it could lead to instability and the ultimate downfall of the regime.

If those hardliners want to test Trump, it’s hard to imagine a more effective strategy than sentencing an American citizen to 10 years in prison on patently absurd charges. The ball is now in Trump’s court.