Frustration over the delay in completing devolution of policing and justice could have pushed disaffected nationalists towards support for dissidents, a decommissioning body warned.
In an unusual move the Independent International Commission on Decommissioning advised Washington to persuade unionists into completing a deal on policing and justice.
Leaked cables describe how members of the arms commission, set up to oversee the destruction of paramilitary weapons, gave detailed updates to top American officials on their progress.
In one meeting, while negotiations on transferring policing powers to Stormont were continuing, they advised the US government to push unionists on the importance of reaching an agreement.
The January 2010 discussion involved the head of the commission John de Chastelain and his three co-commissioners.
The words “strictly protect all four” appear alongside their names.
During the meeting, Ambassador Dan Rooney was told weapons decommissioning had been accomplished to a great extent, but not completely.
A week earlier, the UDA had confirmed it had decommissioned its weapons, following earlier moves by the UVF and IRA.
It was noted that one splinter group, the south east Antrim brigade, had yet to put its weapons
beyond use. Gen de Chastelain suggested progress was being held back by concerns regarding dissident elements within the group.
Later, the discussion moved on to the ongoing negotiations to secure a deal on the transfer of policing and justice powers.
Intensive talks were taking place involving the Dublin and London governments, with unionists stalling on a deal.
At one point in the meeting, co-commissioner Andrew Sens cited concerns from loyalists that they had not reaped the same benefits from the decommissioning process as republicans, including travel to America.
Ambassador Rooney was able to report back that visiting the US was a “powerful carrot” which could influence behaviour.