The U21s are taking part in the European Championship finals in the Czech Republic and several players who have been capped at senior level will be in the squad, in order to get some experience of tournament football.
However, Barkley was in the squad for the World Cup in Brazil last summer and it is thought most likely he will be with the seniors for their pair of June matches, rather than travelling away with the U21s.
But Martinez told Sky Sports News HQ: ???We are not aware about what the final decision is on Ross Barkley. We are working closely with the FA, the England team, and the England set-up.
???At the moment, Ross is developing extremely well. I think, in the last few games, he has been enjoying his football, which is important.
???All we want is our young players to develop and to enjoy their football. That is the only thing that matters.???
Barkley and forward Romelu Lukaku have been linked with possible moves away from Goodison Park this summer but Martinez is unconcerned.
???I think when you get attention to your young players, it is always a positive,??? he said. ???We have got special talents in the dressing room.???
Everton beat Southampton 1-0 on Saturday to make it three Premier League wins in a row, and they are up to 12th in the table and looking on course to finish the season strongly.
Martinez admitted it has been a tricky campaign for his side, who were expected to build on a fifth-place finish last term but were inconsistent earlier in the season, perhaps partly because of their run to the last-16 of the Europa League.
Martinez has received criticism at times and said: ???It has been a very strong learning curve.
???Obviously, we have enjoyed our European experience and we are a completely different team than we were at the beginning of the season.
???We don???t shy away from the expectations, and it is something that we are going to use in a good way, to become a winning team.
???Our history demands success and this season has been finding the right balance between realistic expectation and being able to be ourselves on the pitch.
???I think, as a manager, you need to take criticism if you don???t get results. I will always take responsibility when the results are not going our way and what I always do is look into the dressing room and see the characters we have got, the personalities we have got – they are people who stand up to the challenge.
???With people like that, you are really looking forward to finding solutions and being successful. I think this season we showed that we are ready to face challenges head-on and we are really excited about the future.
???Obviously, we have got seven games left in the league and we are very much concentrating on how many points we can get from now until the end of the season and finishing really strong.???
Martinez was speaking at an open training session which the club holds every season and was delighted to see Everton fans packed in to watch the squad work.
???Over the years, it has been an incredible success,??? he said. ???You get that engagement, days like today allow the players to work in front of our fans.
???Days like this make sense and, as a football club, we come together in a great way.
???To see a young boy with that dream of playing one day for Everton, seeing his heroes training here, it makes the day special.???