Manager Michael O'Neill is hoping to persuade others to follow Scotland-born James McPake's lead in declaring for Northern Ireland.
McPake, 27, qualifies for Northern Ireland via a Coleraine-born grandfather and has opted to transfer his allegiance after failing to earn a Scotland call-up. He is one of four uncapped players in a 24-man squad for the June 2 friendly against Holland in Amsterdam, joining Swansea striker Rory Donnelly, Walsall forward Will Grigg and Burnley full-back Daniel Lafferty.
O'Neill said: "I spend a lot of time researching the available players because we need as many as possible. I have spoken to a number of others and some haven't made that decision at this point in time or aren't willing to change their allegiance at the moment. But we will continue to monitor and strengthen."
Copyright (c) PA Sport 2012, All Rights Reserved.