Cork City goalkeepers Mark McNulty and Alan Smith have been called into the Republic of Ireland training squad, with the uncapped trio of Declan Rice, Kevin Long and Alan Browne also earning call-ups.
West Ham's Rice, Burnley defender Long and Preston North End midfielder Browne are in with a shout of making their competitive debuts over the coming weeks, with a number of senior players to report into camp next week.
O'Neill's side take on Mexico in New Jersey on 1 June and then play two games at the Aviva where they welcome Uruguay to Dublin on Sunday 4 June before taking on Austria in their World Cup qualifier seven days later.
18-year old Rice made his Irons debut against Burnley on Sunday and can play in defence or midfield and earlier this year won the Under-17 International player of the year award.
Preston's Alan Browne was added to the 38-man squad yesterday, while 26-year-old Long has enjoyed spells on loan at both Barnsley and the MK Dons.
The trio will also be joined by Cork City goalkeepers Mark McNulty and Alan Smith for the first of three days training behind closed doors on Wednesday.
Republic of Ireland Training Squad
Goalkeepers: Mark McNulty, Alan Smith (Cork City)
Defenders: Cyrus Christie, Alex Pearce, Richard Keogh (Derby County), Shane Duffy (Brighton & Hove Albion), Andy Boyle (Preston North End), Kevin Long (Burnley) Declan Rice (West Ham United), John Egan (Brentford)
Midfielders: Eunan O'Kane (Leeds United), Alan Browne, Daryl Horgan (Preston North End), Conor Hourihane (Aston Villa), Wes Hoolahan (Norwich City), Stephen Gleeson (Birmingham City), Callum O'Dowda (Bristol City)
Forwards: David McGoldrick (Ipswich Town), Daryl Murphy (Newcastle United)
