MLS said in a statement Messi and Alba would be unavailable for Saturday's clash against FC Cincinnati "due to their absence" at this week's All-Star showpiece.

"Per league rules, any player who does not participate in the All-Star Game without prior approval from the league is ineligible to compete in their club's next match," the league said in a brief statement.

Messi and Alba had both been selected to play for a combined MLS side in Wednesday's game against a team drawn from Mexico's Liga-MX as part of the league's All-Star break.

However both players withdrew from the showpiece early Wednesday for reasons that were not revealed.

The 11th-hour snub left Messi and Alba both facing sanction. Under MLS rules, players selected for the All-Star game must participate unless they have a valid reason -- such as an injury -- not to do so.

MLS commissioner Don Garber said Friday the league had been left with no choice but to suspend players from duty this weekend, describing the ruling as a "very difficult decision".

"I know Lionel Messi loves this league," Garber said. "I don't think there's a player -- or anyone -- who has done more for Major League Soccer than Messi. I fully understand, respect, and admire his commitment to Inter Miami, and I respect his decision.

"Unfortunately, we have a long-standing policy regarding participation in the All-Star Game, and we had to enforce it. It was a very difficult decision."

Garber however said MLS would review its existing policy in future.

"We're going to take a hard look at the policy moving forward," he said. "I'm committed to working with our players to determine how the rule should evolve."

Speaking on Wednesday, Garber said the league should have known earlier about the no-show, but expressed some sympathy for the gruelling schedule faced by Messi in recent weeks.

The 38-year-old Argentinian superstar has played nine games in 35 days and played 90 minutes in each game, including four games in the FIFA Club World Cup.

"Miami's had a schedule that is unlike any other team," Garber said. "Most of our teams had a 10-day break. Miami hasn't. So we have to manage through that as a league."

Messi and Alba's participation in the game had been under a cloud after Miami coach Javier Mascherano indicated last weekend he would have preferred the duo to be excused from All-Star duties.

"The players are called up. I'd prefer they rest, but it's not my decision," Mascherano said.