The 34-year-old striker will reach the landmark in Thursday's Confederations Cup encounter with Nigeria, 11 years after pulling on the light blue shirt for the first time against Saudi Arabia in March 2002.
"It's a matter of pride, being the first player to play all these matches for the Uruguay team," said the former Manchester United and Atletico Madrid striker.
"I saw an article today, and I said the same thing yesterday – through all the things I've experienced in my career, I never imagined I'd be playing my 100th match at the Confederations Cup.
"And the match tomorrow (Thursday) means a lot. Obviously it's 100 matches for me, but it's a key game and we have to win in order to reach the next phase.
"It's a matter of great pride to wear the light blue shirt so many times, and I hope I can continue doing this."
The Brazilian city of Salvador will provide a fitting setting for Forlan's milestone moment.
His father, Pablo, played for Brazilian clubs Sao Paulo and Cruzeiro during his professional career, and Forlan followed in his footsteps by signing for Porto Alegre side Internacional last year.
"For me to play here in this Confederations Cup is an award that was given to me by the national team," Forlan said.
"I've been in Brazil for one year, so I'm very happy to be in a place where my father played. The reception I got in Recife (where Uruguay lost to Spain) was spectacular."
Since spearheading Uruguay to success at the 2011 Copa America, a year after they reached the semifinals of the World Cup, Forlan's form has dipped, and he joined Internacional after an unhappy stint at Inter Milan.
Uruguay are also going through a difficult period, currently lying fifth in South American qualifying for next year's World Cup, but coach Oscar Tabarez said it was unfair to attach blame to Forlan.
"There are too many factors in football to say that a team depends exclusively on one player," he said.
"That's not the case. He's a player who has more influence than normal players, which we know. But footballers are human beings. Sometimes the level of their performances oscillates."
Forlan also expressed support for the protests that have swept Brazil, with hundreds of thousands of people taking to the streets to denounce the lavish amounts of public money that have been spent on the organisation of the Confederations Cup and next year's World Cup.
"I think each person has their reasons for making a protest," he said.
"I believe that this is a moment where everyone is focusing on the World Cup and looking at Brazil, so it's a moment for people to speak up and express their opinions about what is wrong. But who am I to talk about it?"
The game against Nigeria will present Forlan with an opportunity to reclaim Uruguay's outright goal-scoring record, after Luis Suarez drew level with him on 33 goals by scoring a late consolation against Spain.