N90 controller experienced operational error at 4000 ft during vector procedures to lga.

Attributes
ACN	649914
Time
Date	200503
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : lga.airport
State Reference	NY
Altitude	msl single value : 4000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90.tracon
Operator	common carrier : air carrier
Make Model Name	B717 (Formerly MD-95)
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : n90.tracon
Operator	common carrier : air carrier
Make Model Name	Regional Jet 200 ER&LR
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller limited radar : 10 controller radar : 9
ASRS Report	649914
Person 2
Affiliation	company : air carrier
Function	flight crew : captain
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued advisory controller : issued new clearance flight crew : took evasive action
Consequence	faa : investigated
Miss Distance	horizontal : 15000 vertical : 700
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

While working arrival traffic into lga; descending to 3500 ft; I noticed an aircraft level at 4000 ft heading toward my arrival. I issued traffic; gave an immediate descent and turn.

Original NASA ASRS Text

Title: N90 CTLR EXPERIENCED OPERROR AT 4000 FT DURING VECTOR PROCS TO LGA.

Narrative: WHILE WORKING ARR TFC INTO LGA; DSNDING TO 3500 FT; I NOTICED AN ACFT LEVEL AT 4000 FT HEADING TOWARD MY ARR. I ISSUED TFC; GAVE AN IMMEDIATE DSCNT AND TURN.

Data retrieved from NASA's ASRS site as of January 2009 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.