Xiyue Wang and his family celebrate a holiday together in 2015. (Courtesy of Hua Qu)

Two videos that aired on Iranian television over the weekend suggest Tehran is trying to pressure the United States in advance of a potential decision on sanctions and push Britain to repay more than a half-billion dollars for undelivered weapons.

The videos broadcast Sunday focused on a Princeton University graduate student who was conducting historical research in Iran and an Iranian-British charity worker who was visiting family. Both have been sentenced on espionage charges, and their governments and colleagues consider them political pawns.

"What the Iranian government is doing is reprehensible," said Reza Marashi, research director of the National Iranian American Council, noting Iran's hints of interest in a prisoner swap. "But you have to juxtapose it against, how do we bring our people home? We can't just let them languish."

Xiyue Wang, who was researching governance in Persia from 1880 to 1921, was shown on Iranian TV 2 writing what appeared to be a confession, interspersed with footage of the CIA seal and students strolling across Princeton's campus as ominous music suggesting villainy thrummed in the background.

In his English-language comments, however, Wang acknowledged nothing more incriminating than looking at historical archives, talking to a U.S. diplomat about educational programs abroad and opining vaguely that knowledge of the country is "better for (U.S.) policy toward Iran." Wang has been sentenced to 10 years in prison for "infiltrating" the country.

"My husband is completely innocent," said his wife, Hua Qu. "He is just a scholar, just a student, just a history nut."

Demonstrators in London hold placards before a march in support of Nazanin Zaghari-Ratcliffe, the British-Iranian mother who is in jail in Iran. (Peter Nicholls/Reuters)

Daniel Day, an official in Princeton communications, said Wang laid out his research and got help gaining access to Iran's libraries and archives from the Iran Interest Section of the Pakistani embassy.

"He was not involved in any political activities or social activism while he was in Iran; he was simply a scholar trying to gain access to historical records he needed for his dissertation," Day said.

A separate video featuring Nazanin Zaghari-Ratcliffe, who is serving five years, purported to show "proof" that she was training journalists and "opposition cyber teams" to establish a spy network. Her family and co-workers at the Thomson Reuters Foundation have said she was on a personal visit, and was not doing any journalistic work.

The release of the videos comes at a critical juncture for relations between Iran and the two countries, which were among six world powers that negotiated the 2015 deal with Iran to ease some sanctions in exchange for restrictions on its nuclear program. It also underscores the stark difference between the approach to Tehran shown by the British government and the Trump administration.

Britain is considering paying $530 million to Iran to clear an outstanding debt dating from a pre-revolution sale of tanks and other vehicles in the 1970s. Both London and Tehran say the payment is not linked to Zagari-Rat­cliffe's release, and denied it is a ransom. But it is similar to a $400 million U.S. payment to Iran in 2016 to settle another decades-old weapons debt, flying pallets of cash to Tehran only after it released five U.S. citizens, including Washington Post reporter Jason Rezaian.

The United States has no more frozen stashes of Iranian cash to return. But it does have leverage, including the threat of more sanctions and stricter enforcement of the nuclear deal. In October, President Trump refused to certify Iran's compliance with the accord, and asked Congress to attach new conditions that could scuttle the agreement. If Congress doesn't act by its Dec. 12 deadline, Trump said, he would consider withdrawing from it.

Wang's wife said the video's timing was calculated to influence Congress and the White House.

"My husband has literally been used as a political pawn for negotiations on all diplomatic issues between the United States and Iran," she said.

In recent months, Iranian officials have broached a prisoner swap for Iranians in U.S. jails. Besides Wang, at least three other Americans are imprisoned in Tehran: businessman Siamak Namazi and his elderly father, Baquer, and Karan Vafadari, an art gallery manager. Robert Levinson, a former FBI agent, has not been seen since disappearing in Iran in 2007.

Unlike the Obama administration, which had multiple channels to communicate with Iran, the Trump administration has virtually none. The State Department routinely raises the fate of the U.S. prisoners during meetings of a committee formed to discuss concerns involving the nuclear accord. "We continue to call for Mr. Wang and all unjustly detained prisoners to be released immediately," said a State Department official, speaking anonymously under department rules. "We strongly condemn Iran's subjecting Mr. Wang and other prisoners to these forced video appearances."

Marashi said it is harder to negotiate the release of U.S. citizens after Trump's Iran speech in October, in which he cited almost 40 years of grievances and called the regime "murderous" and "sinister."

Marashi said the videos are designed to alert the White House it still wants a prisoner swap.

"If past is prologue," he said, "when they don't see any movement, they turn up the heat a little by doing something."