The 1982 World Cup hero will no longer continue his role of Elite Player Mentor with the IFA due to an overlap of responsibilities
Armstrong was appointed to the role in the summer of 2011 where his duties involved speaking with players who might be deemed 'at risk' of switching to another association, such as the Republic of Ireland, and encouraging them to stay with the IFA.
However, he revealed yesterday that he had done all that he could and that Michael O'Neill, Northern Ireland team manager, would take on the extra responsibilities.
"I have take my remit as far as I could," Armstrong told the Sunday Life. "It had come to the stage where there was an overlap (in duties).
"The role has changed and naturally enough the manager Michael O'Neill is keen to take on the extra responsibility of speaking to players who might be interested in playing for Northern Ireland."
The 58-year-old played 63 times for the Northern Ireland team, scoring 12 goals, including the winning goal against Spain in the 1982 World Cup.