Reuters - An 81-year-old Iranian-American man sentenced to 10 years in prison in Iran on charges he spied and cooperated with the United States has been returned to prison after a short medical leave, his lawyer and son said on Tuesday.

The decision to send Baquer Namazi, a former Iranian provincial governor and ex-UNICEF official, back to prison, despite the advice of the Iranian government�s own medical examiner, is �tantamount to a death sentence,� said Jared Genser, an attorney for the Namazi family.

Baquer Namazi�s son, Babak, told reporters in Washington on Tuesday that returning his father to prison was a �spectacular display of cruelty� by the Iranian government.

Attempts to reach the Iranian judiciary for comment about Namazi were unsuccessful, and a spokesman for Iran�s mission to the United Nations did not respond to a request for comment.

The United States is �deeply disturbed� by the return of Baquer Namazi to prison, and has been alarmed at his declining health, Steve Goldstein, the U.S. undersecretary of state for public diplomacy and public affairs said in a statement.

Namazi�s health has deteriorated over the nearly two years he has been imprisoned in Iran. In January, he was taken to the hospital for a sharp drop in blood pressure and irregular heartbeat and in September he underwent emergency surgery to install a pacemaker, his family has said.

Namazi was granted a four-day medical leave on Jan. 28, which was extended until Feb. 4.

After examining Namazi, the Iranian government�s medical examiner recommended he be granted a three-month leave from prison on medical grounds. The medical examiner�s recommendation was communicated to the Namazi family by phone, Genser said.

But instead of being granted the leave, Namazi was told on Tuesday to report back to Evin Prison in Tehran, the lawyer said.

The Namazi family released a statement by Baquer Namazi thanking his friends and UNICEF colleagues for their support.

�Despite the pain inflicted upon my family and myself, I have not lost hope and continue to pray for the great humanitarian causes for which we have all dedicated our lives,� Baquer Namazi said in the statement.

Namazi�s son, Siamak, an Iranian-American businessman in his mid-40s, was arrested by Iranian security forces in October 2015. Iranian authorities detained Baquer Namazi a few months later when he tried to visit his son. Both are in Evin prison and have denied the charges against them.

Siamak Namazi has been physically tortured in prison, including being shocked with a stun gun, Babak Namazi said.

Babak Namazi called in a statement for U.S. President Donald Trump�s administration to �spare no efforts� to bring his brother and father home.

Reporting by Yeganeh Torbati, writing by Makini Brice; editing by Cynthia Osterman and Jonathan Oatis