The Drug Enforcement Administration led a complex venture called Project Cassandra to tackle the criminality of the Lebanese militant group from 2008 on.
But it is claimed Obama's people threw down a number of roadblocks, effectively paving the way for Hezbollah's illegal activities including cocaine smuggling into the US which agents believe raked in $1billion for the terror group.
DEA agents claim the Obama administration stopped them arresting key figures linked to Hezbollah as an agreement on the Iran nuclear deal approached - and scrapped Project Cassandra entirely once the terms were agreed in 2015.
David Asher, who helped establish Project Cassandra, told
Politico: 'This was a policy decision, it was a systematic decision.
'They serially ripped apart this entire effort that was very well supported and resourced, and it was done from the top down.'
He added that the closer Obama for to finalizing the Iran nuclear deal, the more difficult the DEA's job became.
The weapons agreement was announced in January 2016, which coincided with Project Cassandra officials being moved onto other assignments.
After more than a decade of tensions with the West, Tehran signed a landmark deal with world powers to curb its nuclear activity in exchange for the gradual lifting of crippling economic sanctions.