Northern Ireland face Romania in Bucharest on the 4th September (7:45pm), before returning to Belfast to take on Norway at the National Football Stadium at Windsor Park (7 September at 7:45pm).
Dallas who was a major part of the club's promotion to the Premier League last season, has the opportunity to add to his 44 caps for Northern Ireland, with his most recent outings being the 0-0 draw with the Netherlands and a 3-2 win over Czech Republic.
Northern Ireland, Romania and Norway are joined in League B Group 1 of the Nations League by Austria, a team they faced in the first edition of the competition in 2018.