Mary Rezaian pleads for the Iranian government to release her son, Washington Post correspondent Jason Rezaian, and his wife, Yeganeh Salehi. The two were arrested last week on undetermined charges in Tehran along with two others, one of whom has since been released. (Provided to The Washington Post)

A senior Obama administration official on Tuesday called on Iran to release a Washington Post journalist and his wife, as well as two other Americans who were arrested in Tehran last week without explanation.

“There is absolutely no reason for this to occur,” Wendy Sherman, the undersecretary of state for political affairs, said at a hearing of the Senate Foreign Relations Committee.

The arrest of the Post’s Iran correspondent, Jason Rezaian, who holds U.S. and Iranian citizenship, has raised concerns, Sherman said. She said the State Department has used “the appropriate channels, principally the Swiss,’’ to convey its message to the authorities in Tehran.

The United States and Iran do not have formal diplomatic relations, and Switzerland provides consular assistance in Iran.

Sherman noted that Rezaian had recently been in Vienna, reporting on the high-stakes negotiations with Iran over its nuclear program, the principal focus of Tuesday’s hearing. Rezaian’s wife, Yeganeh Salehi, who is Iranian, is a correspondent for the National newspaper, which is based in the United Arab Emirates.

Washington Post journalist Jason Rezaian and his wife, Yeganeh Salehi, who works for the United Arab Emirates newspaper the National, in Tehran in September. (European Pressphoto Agency)

Committee Chairman Robert Menendez (D-N.J.) said that Rezaian’s reporting is “certainly . . . balanced.” So, he asked, in the midst of the nuclear talks, “how is it that the Iranians detain U.S. citizens for what is . . . nothing of any great consequence?”

He added, “I hope they understand very clearly that actions like these undermine whatever negotiating posture they have at the table.”

One of the people arrested, the husband of a photojournalist, was released Tuesday, according to a relative. The photojournalist remains in custody, the family member said. Their names are being withheld at the request of the family. Both are Iranian American.

Rezaian’s mother issued an appeal on video Tuesday asking Iran to release him and his wife.

Also Tuesday, Sen. Robert P. Casey Jr. (D-Pa.) sent a letter to Secretary of State John F. Kerry expressing his concern about Rezaian’s detention and asking that Kerry “undertake every diplomatic effort to ensure that the Iranian regime does not unjustly punish him and his colleagues for their reporting.”

Sherman’s remarks came at a hearing devoted to discussing the status of the negotiations among Iran, the United States and five other world powers to curtail Iran’s nuclear program. The countries agreed in November on a Joint Plan of Action aimed at reaching a deal to ease sanctions in exchange for ensuring that Iran does not obtain a nuclear weapon.

Menendez and the committee’s ranking Republican, Sen. Bob Corker (Tenn.), stressed that they do not want the negotiations, which have been extended to Nov. 24, to go beyond that date.

“At that point, Iran will have exhausted its opportunities to put real concessions on the table,” Menendez said, “and I will be prepared to move forward with additional sanctions.”

At the hearing, Sherman repeatedly assured the committee that the administration would keep it apprised of the details of the talks and would consult members before agreeing to lift any sanctions, which the government is required to do.

She said there are several criteria for a good agreement, “one that cuts off all of Iran’s potential paths to a nuclear weapon”: limiting Iran’s ability to make plutonium at its Arak reactor, to enrich uranium at its Natanz and Fordow facilities, and to develop a covert nuclear program.

She said sanctions relief would come only after Iran took “verifiable steps” under a comprehensive deal. “Our goal is to structure an agreement that would make any attempt to break out of such an agreement so visible and so time-consuming that Iran would either be deterred from trying or stopped before it could succeed,” Sherman said.

Treasury Undersecretary David S. Cohen said that despite limited sanctions relief since last fall, Iran remains “in a deep economic hole.” The value of the rial has dropped by about 7 percent, and Iran has lost $20 billion in oil revenue in the past six months and stands to lose $15 billion more in the next four months.