Lionel Messi extended his remarkable goal-scoring streak as Inter Miami powered into the final of the Leagues Cup with an emphatic 4-1 victory over Philadelphia Union on Tuesday.

The Argentina superstar took his tally to nine goals in six appearances for Miami in an entertaining semi-final at Philadelphia's Subaru Park.

Venezuelan international Josef Martinez, Messi's former Barcelona team-mate Jordi Alba, and substitute David Ruiz scored Miami's other goals, with Alejandro Bedoya the lone scorer for outgunned Philadelphia.

The result leaves Messi preparing for the 42nd final of his career with Miami facing Nashville SC in Saturday's final of the World Cup-style tournament for teams from Mexico and Major League Soccer.

Nashville booked their place in the final later Tuesday with a 2-0 win over Mexican side Monterrey and will host the final this weekend.

Miami meanwhile were left basking in a victory which also sees them qualify for the CONCACAF Champions Cup regional tournament next season – potentially opening up a route into FIFA's expanded Club World Cup in 2025.

"Our goal was to qualify for international competition next season and we've done that tonight," said Miami head coach Gerardo 'Tata' Martino.

"This most important thing was achieving qualification for Concacaf Champions Cup, and now we have to prepare to win this tournament, which has us feeling very motivated and confident."

Miami's semi-final in Philadelphia was in theory supposed to be the toughest assignment yet faced by Messi since he made his debut for Miami on July 21 after joining from Paris Saint-Germain.

Philadelphia are one of the strongest teams in MLS, and are third in the Eastern Conference standings while Miami are bottom of the table.

The Union have also been practically invincible at home, losing only once in their previous 38 games at Subaru Park.

But the home side were left in disarray just three minutes after kick-off as Miami took the lead.

A long ball forward from Ukrainian defender Sergii Kryvtsov sowed panic in the Union back line, and Martinez latched onto the pass before rifling a shot past diving Philadelphia goalkeeper Andre Blake.