Bellamy's preparations for this international camp has been hit with several injury absences including key man Harry Wilson.
A return to League A is a reward for Wales' strong form in the last Nations League campaign, but they face a tough test up against Jorge Jesus' all-star side in Lisbon.
Wales' form has dipped in the last 12 months as they chase a first win since last November's World Cup qualifying victory over North Macedonia.
"Obviously they're the best players in the world at the end of the day, you can't really sugar coat it," James said.
"They've got Champions League winners, they've got these kinds of things.
"I think we're always underdogs. We're used to it, so hopefully we can use that to benefit ourselves.
"You can't count us out. We've got a puncher's chance at the end of the day and we're going there to sort of cause an upset."