Raed Saleh speaks at the Supporting Syria & the Region Conference in London, 4 February 2016. Screenshot/YouTube The head of Syria's Civil Defense Units, also known as the White Helmets, said he was denied entry into the US upon arriving in Washington, DC, from Turkey to receive a humanitarian award.

Raed Saleh, 33, said he flew from Istanbul to Dulles airport on Tuesday. He was set to receive a humanitarian award from InterAction, an NGO based in Washington, DC, for his work with the White Helmets — an organization of more than 2,800 volunteers that respond to bombings against civilian communities in Syria.

The group says that more than 40,000 people have been rescued by volunteers working with the Civil Defense Units. The volunteers receive a $150-per-month stipend to don their White Helmets and dig people out from beneath the rubble of barrel bombings.

But Saleh — who was nominated for the 2016 Humanitarian Award by the non-profit Relief International and addressed the UN Security Council just last year in New York about the White Helmets' humanitarian work — said he was told by customs agents to "go back where he came from" when he arrived in DC on Tuesday night.

"When I arrived in Washington, DC, they told me my visa had already been canceled so I should go back to Turkey 'where I came from,'" Saleh told Business Insider in an email on Tuesday.

Saleh, a former businessman who sold electrical equipment before the civil war erupted in 2011, said that the United States Agency for International Development (USAID) called him when he arrived back in Istanbul and apologized for what had happened.

USAID has provided the White Helmets with $20 million in monetary aid since 2013.

People and Civil Defense members carry a dead body removed from a destroyed Medecins Sans Frontieres (MSF) supported hospital hit by missiles in Marat Numan, Idlib province, Syria, February 16, 2016. Ammar Abdullah/Reuters However, Saleh and his colleague Zouheir Albounni, who works for a USAID implementer that provides support to the White Helmets, told Business Insider that Saleh's visa was not set to expire until September 2016. He also had not been notified by anyone prior to boarding his flight in Istanbul that his visa had been canceled or expired, they said.

Albounni, who was scheduled to be Saleh's translator for Tuesday's event at InterAction, said he "has no idea" why Saleh was denied entry.

"From everything I know, Raed has a valid visa to the States, and this is not his first time here," Albounni told Business Insider. Additionally, Albounni said, "Raed was holding a letter from USAID addressing customs and immigration to facilitate his entry, given that the Syrian Civil Defense is USAID/OTI's largest partner in Syria."

OTI is USAID's Office of Transition Initiatives.

US government officials have not responded to requests for comment from either Relief International or InterAction, which condemned the decision to bar Saleh from entering the country.

"InterAction has continually warned of the consequences of policies that prevent humanitarian professionals from freely traveling, as any other modern global professional must to be effective," InterAction CEO Sam Worthington said in a statement.

"If the US government won't allow Raed to be honored in person by the humanitarian community in Washington then InterAction leaders will travel to Raed, on the border of Syria, to ensure his work is appropriately and personally acknowledged," he continued.

USAID representatives didn't immediately respond to a request for comment from Business Insider.

Residents and civil defense members look for survivors at a damaged site after what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad in the Al-Shaar nighbourhood of Aleppo, Syria September 17, 2015. Abdalrhman Ismail/Reuters Saleh, who has two children, began organizing peaceful demonstrations in his home town of Jisr Ashughour, Syria, after protests broke out against the regime of Syrian President Bashar al-Assad in 2011. He was forced to flee to Turkey later that year after Assad's army entered his town, but returned to Syria's Idlib province in 2012 where he has organized 20 separate teams of civil defense volunteers since June 2013.

Though Saleh was unable to attend Tuesday's ceremony, he prepared remarks about the White Helmets' work that were read on his behalf.

"We are the Syrian civil defense, the 'White Helmets,'" Saleh wrote. "We confirm our commitment to perform our duty and provide services without discrimination and with respect for the human rights endorsed by the humanitarian organizations in the United Nations. We have saved over 40,000 lives. We are on the side of life."