The 25-year-old will team up with his Bafana Bafana team-mates ahead of their friendly against the USA next Wednesday, November 17.
Somma, born in South Africa before he moved to the United States, this week signed a new three-year deal at Elland Road.
He has scored seven goals in 13 appearances after breaking through into Simon Grayson's first-team squad this season.
The former Perugia and San Jose forward fired nine goals in 14 games for Lincoln while on loan there last season.
Source: PA