American trialist Devann Yao had had a successful trial with Championship Ipswich.
The 19-year-old striker has already spent most of his footballing career in Europe.
He started out at 13 with Metz before spells with Livorno and St Mirren.
He has now trained with Ipswich and impressed during a behind-closed-doors game with Celtic where he scored one and set the other up in a 2-2 draw.
"Devann did well. He had lots of energy and can be pleased with his performance," boss Roy Keane said.
"He had a hand in both goals, and hopefully we can do something. We will offer him a contract."