How to widen too small door opening for front door in basement wall (Leca)

[fabian2000]

Going to replace an exterior door in our basement. The opening is about 20x9 but I want a door with frame dimensions of 21x10.
The wall construction is Leca/lightweight concrete.

Assuming it's possible to widen and there's no load-bearing beam, how can I do it the cheapest and easiest way?

Reciprocating saw blade for this?
Hand saw for this?

 

[Liteavvarje]

Just cut up, what might cause trouble is that above the current door there is a lightweight concrete/cement beam which functions to relieve the hold where the door is, it's a bit difficult to place a relief higher up, but it can be done. Then you might need help with that.