Update - 12.53pm: Republic of Ireland manager Martin O'Neill has confirmed that Harry Arter is taking a break from international football.
The Cardiff midfielder is not in the squad for the upcoming internationals against Wales and Poland.
Last week O'Neill revealed that the Cardiff midfielder had an altercation with assistant boss Roy Keane in June but claimed the situation had since been 'defused'.
But today the manager has conceded it may be a factor in Arter's absence.
Speaking at a press conference in Dublin today, O'Neill said: "That might be part of the reason, yes it could well be if that's the case.
"But he's got a number of things to consider, obviously."
O'Neill said Arter's loan move to Cardiff was also a reason behind his decision.
He said: "Harry's not coming, he's concentrating on his club football at this moment. I think he wants to just get back on track.
"His club appearances have been few and far between just recently and he wants to concentrate on that."
O'Neill denied reports that Declan Rice's decision to make himself unavailable amid England's interest in him was also down to a clash with Keane, and revealed he has not had further talks with the player.
O'Neill said: "No, I've not spoken with Declan recently. I've obviously spoken with the family, but Declan is taking a little bit of time.
"Declan is a young fellow, 19 years of age. Obviously we are very, very keen to have him.
Harry Arter has been left out of the Republic of Ireland squad for the upcoming games with Wales and Poland.
The midfielder played for Cardiff in their 3-2 defeat to Arsenal yesterday and has reportedly asked not to be included in Martin O'Neill's Ireland squad.
Arter had a dispute with assistant Roy Keane this summer but O'Neill said last week that the situation has since been defused.
Shane Long also misses the trip to Cardiff due to a foot injury he picked up in Southampton's win against Crystal Palace at the weekend.
The Republic play Wales in their opening Nations League game on Thursday, before meeting Poland in a friendly next Tuesday.
Injuries have also ruled out James McCarthy (leg), Robbie Brady (ankle), Scott Hogan (groin) and Sean Maguire (hamstring), while Kieran O'Hara will link up with the Under-21s for two crucial qualifiers against Kosovo and Germany.
Republic of Ireland Squad
Goalkeepers: Colin Doyle (Hearts), Sean McDermott (Kristiansund BK), Darren Randolph (Middlesbrough)
Defenders: Seamus Coleman (Everton), Cyrus Christie (Fulham), Matt Doherty (Wolverhampton Wanderers), Shane Duffy (Brighton & Hove Albion), Richard Keogh (Derby County), Ciaran Clark (Newcastle United), Kevin Long, Stephen Ward (Burnley), John Egan, Enda Stevens (Sheffield United)
Midfielders: Alan Judge (Brentford), Jeff Hendrick (Burnley), Conor Hourihane (Aston Villa), Alan Browne (Preston North End), Shaun Williams (Millwall), David Meyler (Reading), Daryl Horgan (Hibernian), Callum O'Dowda (Bristol City), James McClean (Stoke City)
Forwards: Jonathan Walters (Ipswich Town*), Graham Burke, Callum Robinson (Preston North End), Aiden O'Brien (Millwall)