The news was first reported by Diario Gol, saying that Haas had been in touch with the McLaren-driving Spaniard as a potential replacement for Romain Grosjean - who may move to Ferrari.
"Alonso to Haas? That's the first I've heard of that," Haas team boss Gunther Steiner told BT newspaper.
"I think we can definitely reject that."
The 2018 season continues tomorrow with the Chinese Grand Prix.