Republic of Ireland boss Martin O'Neill says Harry Arter is "concentrating on club football" after the midfielder was absent from the squad to face Wales.

O'Neill revealed last week that Arter, 28, was involved in an altercation with assistant boss Roy Keane in the summer.

"That might be part of the reason, yes it could well be if that's the case," O'Neill said on Monday as he named his final squad for the Nations Cup game.

Southampton striker Shane Long misses out because of a foot injury.

"I'm not denying there hasn't been altercations," O'Neill told the Daily Mirror last week but he added that the situation has "definitely been defused".

Arter played the full game for Cardiff on Sunday in a 3-2 defeat by Arsenal in the Premier League.

"Harry's not coming, he's concentrating on his club football at this moment. I think he wants to just get back on track," said O'Neill on Monday.

"His club appearances have been few and far between just recently and he wants to concentrate on that."

O'Neill has trimmed his panel down from 31 to 26 for Thursday's game in Cardiff and a friendly against Poland on 11 September,

Defensive pair Darragh Lenihan and Greg Cunningham also miss out along with goalkeeper Kieran O'Hara, who will link up with the U21s.

Preston striker Callum Robinson and Norway-based goalkeeper Sean McDermott remain the squad after being handed first senior call-ups by O'Neill.

Northampton-born Robinson, 23, qualifies for the Republic through his maternal grandmother, who is from Monaghan.

McDermott, who plays for Kristiansund, has represented the under-21s.

Robbie Brady, Scott Hogan, Sean Maguire and James McCarthy are all also unavailable because of injury.

Republic of Ireland squad

Goalkeepers: Doyle (Hearts), McDermott (Kristiansund BK), Randolph (Middlesbrough)

Defenders: Coleman (Everton), Christie (Fulham), Doherty (Wolves), Duffy (Brighton), Keogh (Derby County), Clark (Newcastle United), Long (Burnley), Ward (Burnley), Egan (Sheffield Utd), Stevens (Sheffield United),

Midfielders: Judge (Brentford), Hendrick (Burnley), Hourihane (Aston Villa), Browne (Preston), Williams (Millwall), Meyler (Reading), Horgan (Hibernian), O'Dowda (Bristol City), McClean (Stoke City)

Forwards: Walters (Burnley), Burke (Preston), Robinson (Preston), O'Brien (Millwall)