ZNY controller experienced a loss of separation event when failing to note conflicting opposite dire...

Narrative:

Air carrier X was southwest bound on J121 at flight level 180. Aircraft Y was northeast bound on V139 (same airway as J121) at 17;000 feet. Air carrier X was descended from flight level 180 to 14;000 feet to maintain separation with a ewr departure that was climbing above air carrier X. Unfortunately this descent clearance caused a loss of separation with aircraft Y. Conflict alert went off very late and I attempted to then turn both aircraft to avoid a mid-air collision. Both pilots were; at the same time; trying to tell me that they were responding to TCAS resolution advisories. I believe both flights responded to my turn clearances as well as responding to their TCAS RA's. Conflict alert should definitely have gone off earlier. This would have at least helped me avoid the near mid-air collision.

Original NASA ASRS Text

Title: ZNY controller experienced a loss of separation event when failing to note conflicting opposite direction traffic prior to issuing a descent clearance; reporter listed the late Conflict Alert notification as a contributing factor.

Narrative: Air Carrier X was southwest bound on J121 at flight level 180. Aircraft Y was northeast bound on V139 (same airway as J121) at 17;000 feet. Air Carrier X was descended from flight level 180 to 14;000 feet to maintain separation with a EWR departure that was climbing above Air Carrier X. Unfortunately this descent clearance caused a loss of separation with Aircraft Y. Conflict alert went off very late and I attempted to then turn both aircraft to avoid a mid-air collision. Both pilots were; at the same time; trying to tell me that they were responding to TCAS resolution advisories. I believe both flights responded to my turn clearances as well as responding to their TCAS RA's. Conflict alert should definitely have gone off earlier. This would have at least helped me avoid the near mid-air collision.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	890639
Time
Date	201005
Local Time Of Day	1201-1800
Place
Locale Reference	ZNY.ARTCC
State Reference	NY
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Aircraft 2
Make Model Name	Light Transport Low Wing 2 Turbojet Eng
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict

ZNY controller experienced a loss of separation event when failing to note conflicting opposite direction traffic prior to issuing a descent clearance; reporter listed the late conflict alert notification as a contributing factor.