Firmino converted Trent Alexander-Arnold's superb near-post cross to break Monterrey's hearts and set up a meeting with Copa Libertadores winners Flamengo in Saturday's (December 21) final.

Naby Keïta gave European champions Liverpool the lead in the 11th minute at the Khalifa International Stadium.

Monterrey, winners of the Confederation of North, Central American and Caribbean Association Football Champions League, drew level shortly after through Rogelio Funes Mori.

That was how it stayed until Brazilian Firmino's deft touch in the first minute of added time gave Liverpool a victory their performance hardly deserved.

Mexican side Monterrey frustrated pre-tournament favourites Liverpool, who lifted the UEFA Champions League trophy in June, and will feel they did enough to book a place in the final.

They were met with stern resistance from Liverpool goalkeeper Alisson, who thwarted Monterrey on several occasions throughout the match.

Liverpool, forced to field midfielder Jordan Henderson at centre-back in the absence of Virgil van Dijk through illness, had chances of their own, but were unable to edge in front until stoppage time.

"It was a bit different in defence," Henderson said.

"Most important thing was the win, we defended well for the majority.

"Overall we have to be delighted with how things went."