US: Iran's government make no sufficient efforts to prevent human trafficking

US Trafficking in Persons Report 2016 says Iranian officials are involved in the coerced recruitment and use of Afghan men for combat in Syria

 The US State Department has issued its annual 'Trafficking in Persons Report 2016' on 30 June 2016.
The report puts Iran in the lowest Tier 3 of its four-step classification of countries. Iran has been classified in the lowest category since 2009.
Other Tier 3 countries include North Korea, Russia, Sudan and Syria.

allowing is part of US State Department's annual 'Trafficking in Persons Report 2016' about Iran:

Iran government made minimal efforts to prevent trafficking…

IRAN: Tier 3
 Iran is a source, transit, and destination country for men, women, and children subjected to sex trafficking and forced labor. Accurate information on human trafficking in Iran is difficult to obtain. Organized groups reportedly subject Iranian women, boys, and girls to sex trafficking in Iran and in Afghanistan, the Iraqi Kurdistan Region, Pakistan, United Arab Emirates, and Europe. Iranian girls between the ages of 13 and 17 are targeted by traffickers for sale abroad…
An increase in the transport of girls from and through Iran en route to other Gulf States for sexual exploitation has been reported from 2009-2015; during the reporting period, Iranian trafficking networks subjected Iranian girls to sex trafficking in brothels in the Iraqi Kurdistan Region…In Tehran, Tabriz, and Astara, the number of teenage girls exploited in sex trafficking continues to increase.
Organized criminal groups kidnap or purchase and force Iranian and immigrant children to work as beggars and street vendors in cities, including Tehran. These children, who may be as young as 3, are coerced through physical and sexual abuse and drug addiction; reportedly many are purchased for as little as $150.
In January 2016, an international organization reported the Iranian government and the Islamic Revolutionary Guards Corps (IRGC) coerced male Afghans resident in Iran, including migrants and refugees, to fight in military brigades deployed to Syria by threatening them with arrest and deportation to Afghanistan. Afghan boys in Iran are vulnerable to sexual abuse by their employers and harassment or blackmailing by the Iranian security service and other government officials. Traffickers subject Afghan migrants, including boys, to forced labor in construction and agricultural sectors in Iran. Trafficking networks smuggle Afghan nationals living in Iran to Europe and force them to work in restaurants to pay off debts incurred by smuggling fees.