The World Cup in November will be Messi's last, he said.
In four World Cups with Argentina, the 35-year-old Paris St-Germain forward has scored six goals and made five assists.
The World Cup is the only trophy missing from Messi's collection.
He said it would be his final World Cup.
Speaking to ESPN, Messi added: "I'm counting down the days to the World Cup. There is anxiety and nerves at the same time. Wanting it to be now, what is going to happen, and ultimately, how is it going to go?"
Messi made his international debut in 2005 and went on to score 90 goals for Argentina.
The previous record for an Argentina player was held by Diego Maradona.
Group C at the World Cup includes Saudi Arabia, Mexico, and Poland, with Argentina facing them.
Anything can happen in a World Cup. The matches are very hard to win. The favorites don't always win.
Argentina is always a candidate because of its history. We are not the favorites because of the time we are in. There are other teams above us.