"The time of my retirement is getting closer and closer," Casillas told reporters.
"It's clear that time passes everyone and I am no exception of that.
"But I have hope and I would like to be with this team full of youngsters. I don't know if it's my last year with Spain, I only think about enjoying each day."
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Casillas went level with Latvia’s Vitalijs Astafjevs in the continent's record books after his 166th appearance in his 16th international season.
The former Real Madrid keeper, who has not conceded a goal in 710 minutes for Spain, made his senior international debut on June 3, 2000 against Sweden when he was 19 years and 14 days old.
He has gone on to win Euro 2008 and 2012, the 2010 World Cup as well as five Spanish league titles with Real and three Champions Leagues.
He left Real last year to join Porto but has been first choice for Spain coach Vicente Del Bosque during the Euro 2016 qualifying campaign, playing in seven of 10 matches despite Manchester United's David De Gea pushing for a starting spot.
"I am happy to reach 166 games and be the player with the most games for the national team," Casillas said.
"In these years I have lived good times and bad times, but I will stick with the good ones."
(Reporting by Angel Krasimirov. Editing by Patrick Johnston)
