Harry Arter said he and the Republic of Ireland support Declan Rice, who chooses between his international future in Ireland or England.
Rice, 19, this week described the decision "as one of the hardest I will ever have to do".
Born in London, Arter as Rice played low for Ireland before making his senior debut in 2015.
And he sympathized with the growing dilemma of West Ham during his speech on Game On RTÉ 2fm
"The manager gave him full respect, leaving him behind the team, supporting him all the time and I know that as a team we do the same," said Arter.
"Declan is a young boy, he is the best player, someone who reaches such a high level as he wants, in my opinion, his attitude and work ethic are incredible: now you see many young players with such skills, but probably not to realize what you need, to get to the top.
"Declan seems to be a very old school in his beliefs and upbringing, if he chooses England, it will be a huge loss for us, it can not be denied, but as I say it is difficult for players when they have two countries, have strong feelings for.
"As I say, I know that as a team we supported him and as a friend I will support him."
Arter also revealed that he did not bring his club form to the international arena – something he would like to volunteer for.
"I just want to try and start acting after choosing what was probably my biggest disappointment during my stay in Ireland, I do not think I will perform anywhere near as good as I can.
"There are no excuses, I have to take responsibility for not putting my club football on the international stage.
"I've made a huge change in my life by moving to Cardiff, I do not want to get into that situation too much, I said what I need to say about it, then I felt it was the best decision to do for myself and the team."
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