ZSU Controller described a TCAS RA event involving VFR traffic departing TJIG and and IFR traffic inbound to TJSJ; the reporter noting combined positions; coordination requirements and VFR departures as causal factors.

Narrative

While [I was] working the R-1/R-5 position. An A320 was inbound to TJSJ on a 150 heading; leveled at 030 FT; expecting the clearance for the ILS8. Mean while VFR traffic; a Citation from the TJIG airport; departed westbound requesting an IFR clearance into MDJB. I was busy with the multiple departures and inbounds; the position should have been split; but as it has been usual for the past months to be short on controllers; and so it was combined for about 30 minutes. I heard the Citation called me on the frequency; instantly I replied to maintain VFR at or below 025; I glanced at the TJIG area and saw a VFR target moving pretty fast; so I knew it was him. I was still busy and kept working. A few seconds later I noticed the VFR traffic too close to the A320 and at 030. I gave a traffic call to the A320; which should have been a traffic alert but it took me a second to think about the correct phraseology and noticed that it was too late. The A320 didn't answer; I noticed he climbed to 035. I kept working; when the A320 told me he responded to a RA; I told him that I gave him the traffic call but he didn't answer; he was probably already responding to the RA. There where multiple contributing factors to this situation. First the two positions where combined and it was busy. Second; the TJIG Contract Tower was closed a few days ago; therefore those pilots depart VFR and pick up IFR in the air; which is a risky thing to do considering how close the final approach courses for both TJSJ runways are from the TJIG airport. Even though is risky; they run out of options since our frequency cannot hear them when they are on the ground so we can issue and IFR clearance prior departure. And third; I was constantly coordinating with the TJSJ Tower; which made the situation a little more complex. It is imperative that TJIG is opened as soon as possible. There are NOTAMs restricting VFR aircraft at or below 020 when heading westbound out of the TJIG airport; but not all of the pilots comply.