The 21-year-old has been a key figure for the Reds this season, scoring in draws against Derby County and Bristol City.
Finland are second in qualifying group 8, a point ahead of Romania, who have a game in hand. The winners of each group qualify directly for next summer's tournament, in Italy and San Marino, while the four best second-placed teams go into a play-off.
The game takes place in Voluntari on Thursday.
Halme's club-mate Ben Williams is in the Wales squad to face Bosnia Herzegovina in Wrexham on Tuesday, along with Sheffield United's Rhys Norrington-Davies, who is on loan at League One Rochdale.
Wales are bottom of group nine, a point behind Tuesday's visitors.
The Championship goes on a two-week break for internationals after the weekend, when Barnsley host Stoke City, the only team below them in the table.