Tottenham striker Kane has been in stunning form and a hat-trick in the 4-3 win over Leicester City last weekend took him to 19 Premier League goals this term.
Kane's rise to prominence was capped by last week's call-up to England's senior team, with Roy Hodgson selecting him for his squad for the Euro 2016 qualifying fixture against Lithuania on Friday and Sunday's friendly in Italy.
Hodgson could be headed for a collision course with Tottenham as he wants Kane to represent the Under-21 side in the Czech Republic later this year, with Spurs fearing his selection could lead to burnout.
However, Chelsea centre-back Cahill says Kane should answer the call should he receive it and spoke about how his experience of featuring at the Under-21 European Championship in 2007 aided his development.
"When you're asked to play for England's seniors or the Under-21s you want to go and play," he said, "I'm sure he's [Kane] not different.
"When it comes to that time [when he might get the call-up] I'm sure he'll accept. He's had a taste of the seniors and there'll be more squads he'll be part of.
"It's important for us that the Under-21s do well at the Euros this summer. They have a good squad and their ultimate aim is the senior squad. I went to the Under-21s finals and it gives you experience as a player. It's good for the players' development."
Kane trained with the senior squad for the first time on Tuesday and Cahill has been impressed by what he has seen.
"[He's been] really good, I've played against him three times this season and he's a handful," he added.
"He's had a fantastic season. He can hold the ball up, run in behind, he has two good feet - so he's got all the attributes.
"To score a hat-trick before joining the squad is ideal. His confidence must be sky-high. He's still a young boy and the first time in the full squad all a bit daunting, but his confidence is sky-high."
Manchester United midfielder Michael Carrick backed Kane to have a big future, saying: "The progress has been sensational. Right from the start of the season he's improved and the level he's at now he's gone up two or three levels.
"Impressively as the spotlight has grown and the expectation, he's grown and performances have improved. That's a really good sign. It doesn't look like a one-off season he looks the real deal. I'm sure he's got a big future ahead of him."
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