The 24-year-old has earned rave reviews for his performances for the Danish side over the past couple of years and claims the Hammers are keen to strike a deal.
However, the Croatian accepts he would be unable to obtain a work permit at the current time because he has never played at senior international level.
Ipsa is therefore prepared to take on a new nationality with Slovenia, who unlike Croatia are members of the European Union.
Such a move would increase the chances of Ipsa joining Avram Grant's side, while he would also like to play for Slovenia.
"Because I haven't played any games for the Croatian senior team and because I'm not an EU citizen, my transfer to West Ham United wasn't completed," the former Energie Cottbus player told Nogomania.
"That is why I'm thinking about becoming a Slovenian citizen. Slovenia is my second home, my grandmother is from Slovenia and I regularly visit this country.
"A few years ago I didn't get a new passport, but now I am again working towards this goal and things are looking pretty good.
"Would I also like to play for Slovenia? Why not. I was never called to the Croatian national team even though I was captain of the Under-21 team.
"But let's not talk too much about this. If I do get Slovenian citizenship, then I could start to think about playing for Slovenia, but the doors to the Croatian national team are obviously closed for me."