Rubio pointed to a Christian pastor who is expected to be executed by Iran's government for abandoning Islam as an example the growing violations in the Shiite-ruled country.

"In recent years, there has been a very troubling increase in religious persecution in Iran," wrote Rubio. "This is true for anti-Christian efforts, but it has also been evident in the repression of non-Shiite Muslims."

Rubio also demanded that the Obama administration call for the pastor's release.

"Our own State Department should call for his immediate release," said Rubio. "These are the moments when the government of this great nation must not be silent, and must be a voice for freedom for those who are defenseless. [I] urge the administration to relentlessly call for an immediate and unconditional release for Pastor Nadarkhani."