The Reds, winners of the 2018-2019 Champions League, will face Copa Libertadores holders Flamengo in Saturday's final at Khalifa International Stadium in Doha, reports Efe news.
Liverpool dominated in the early going Wednesday and while the Liga MX side focused on maintaining their defensive shape, their efforts weren't enough to stop Naby Keita from giving the Reds the lead in the 12th minute off a beautiful pass from Mo Salah.
But, instead of falling back, Monterrey flew forward and their initiative was rewarded with an equaliser just two minutes later.
The sequence leading to the goal began with a foul by Liverpool's James Milner against Rodolfo Pizarro. The resulting free-kick reached the area and ended up on the foot of Monterrey's Jesus Gallardo.
Reds goalkeeper Allison made the initial stop, yet the rebound fell to Rodrigo Funes Mori and he hammered home from close range to level the match at 1-1.
Monterrey goalkeeper Marcelo Barovero did well to stop Milner in the 23rd minute, while Reds keeper Alisson had to be sharp to deny Dorlan Pabon and Funes Mori as Monterrey exploited the absence of the ailing Virgil van Dijk from the Liverpool back line.
Andrew Robertson had a chance to reclaim the lead for the Reds in the 48th minute, two minutes before Pabon forced another save from Alisson.
The Liverpool keeper was also tested again by Funes Mori and Pabon squandered an opportunity.
Tempers frayed in the 76th minute when Liverpool defender Joe Gomez already on a yellow card was cited for a handball. Monterrey coach Antonio Mohamed's heated demands for a penalty earned him a yellow and Reds manager Jürgen Klopp likewise picked up a card for leaving his technical area to argue with his counterpart.
Anxious to avoid extra time as Liverpool girds for the Premier League's holiday marathon, Klopp used his three substitutions to add starters he had been hoping to rest.
The first to come on was Sadio Mane, in the 68th minute, followed seven minutes later by Trent Alexander-Arnold. Firmino replaced Divock Origi in the 85th minute.
A minute into stoppage time, Salah eluded two defenders and advanced the ball to Alexander-Arnold, who found Firmino at the near post for the game-winner.
( With inputs from IANS )