By Yeganeh Torbati

WASHINGTON (Reuters) - A resolution calling for Iran to release two U.S. citizens imprisoned there for months will be introduced on Wednesday by House of Representatives Foreign Affairs Committee chairman Ed Royce, a Republican, and Democratic Representative Gerry Connolly, their offices said.

The resolution will call for Iran to immediately and unconditionally release businessman Siamak Namazi and his father, Baquer Namazi, 80, both of whom have dual citizenship. The text of the resolution was seen by Reuters.

It will also call for U.S. President Barack Obama to undertake efforts to secure their release.

Siamak Namazi was detained by the Islamic Revolutionary Guard Corps in October while visiting relatives and has been barred from leaving Iran since July 2015. His father was arrested in Tehran in February.

"Iran's continued wrongful jailing of Americans is very disturbing," Royce said in an emailed statement on Tuesday. "Siamak and Baquer Namazi deserve to be free and with their families, and this resolution should push President Obama to step up efforts to bring them home."

The resolution "encourages the President to utilize appropriate measures" against Iran's government if the Namazis are not released, but it stops short of calling for economic sanctions, a specific request by a representative of the Namazi family, said one source familiar with the resolution who declined to be named.

Siamak Namazi has criticized sanctions against Iran, writing in a 2013 opinion piece in the New York Times that Western sanctions had blocked medicines from reaching the country.

U.S. State Department spokesman Sam Werberg said the agency does not comment on resolutions before they have been formally introduced. He added, "We are not aware of any charges against either Siamak or Baquer and we believe that both reported detentions are unjust."

Five American citizens were released from Iranian prisons in January as part of a prisoner swap with the United States.

Iran has detained several other dual nationals since that swap, including Homa Hoodfar, a Canadian-Iranian woman, Nazanin Zaghari-Ratcliffe, a British-Iranian woman and project manager with the Thomson Reuters Foundation, and Nazak Afshar, a French-Iranian woman.

(Additional reporting by Arshad Mohammed in Washington)