WASHINGTON (AP) — The top U.S. nuclear negotiator says she is concerned by reports Iran has arrested four journalists, including three Americans.

Wendy Sherman says Tehran should release them immediately.

Iran confirmed last week it detained the journalists.

The Washington Post said its correspondent, Jason Rezaian, and his wife were detained in the Iranian capital. The newspaper said Rezaian, 38, holds both American and Iranian citizenship.

His wife, Yeganeh Salehi, is an Iranian citizen who has applied for U.S. permanent residency and works as a correspondent for a newspaper based in the United Arab Emirates. The other two American photojournalists have not been identified.

Sherman testified Tuesday on nuclear negotiations with Iran before the Senate Foreign Relations Committee.