An embarrassing play-off defeat to North Macedonia on home soil saw Italy miss out on Qatar 2022, having also failed to reach the Mundiale four years ago after another play off loss to Sweden.
Italy emerged victorious at last summer's European Championships, meaning they are the highest profile team to miss out in Qatar.
Mancini's men have however salvaged some pride by qualifying for next summer's Nations League finals after a 2-0 win against Hungary saw them top a group that also included Germany and England.
The next edition of the FIFA World Cup will be held in the USA, Canada and Mexico, and Mancini is already preparing his charges to bring home the trophy for the first time since 2006.
"Winning with the national team is the best thing there can be," he said at an event in Rome.
"Giving Italians such joy is incredible, now we have to wait four years. We will aim to win the next World Cup in America.
"We are working, unfortunately we will suffer until December - the disappointment of not qualifying for the World Cup does not pass me.
"It was totally unfair, but the defeats must be faced. We did not deserve to stay out of the World Cup, but unfortunately, that's how it went."
