As the goals piled up for Haji Wright, a rising star for the United States’ under-17 national team, the biggest question was whether he would continue his development in M.L.S. or leave for Europe.

On Saturday, Wright committed to begin his professional career in the United States, but he will do so with the New York Cosmos of the North American Soccer League, according to people familiar with the deal.

The Cosmos are expected to formally announce the signing of Wright — a former Los Angeles Galaxy academy player who turned 17 on Friday — as early as Monday. He is expected to train with the Cosmos’ first team immediately. The N.A.S.L. regular season opens on Saturday with four matches, including a visit by the Cosmos to the Fort Lauderdale Strikers.

The signing of Wright is the latest signal from the Cosmos and the N.A.S.L., officially the second tier in the American soccer pyramid, that the league intends to compete with M.L.S. for players, fans and attention. M.L.S. had fired its own shot in that battle last week by announcing that it would accept an existing N.A.S.L. club, Minnesota United F.C., as an expansion team in 2018.