The Tottenham midfielder has become a key figure for the national team less than two years after making his debut, and will be expected to shoulder even more responsibility in the wake of Wayne Rooney's international retirement.
Dele is an exciting player and it's a great opportunity for him to kick on, but there's always a challenge," said the England manager.
"He's a young player, but he's not a proven player. At the moment, he hasn't won anything.
"Like all young players, he's got to keep looking to improve. His goalscoring record over the past couple of years is phenomenal for a player who is not an out-and-out striker."
Alli is yet to win a trophy during his two years with Spurs but played a pivotal role as Mauricio Pochettino's team finished runners-up to Chelsea last season.
Tottenham tackle Burnley at Wembley on Sunday afternoon in their last game before the international break.
England play World Cup Qualifiers in Malta on Friday and against Slovakia three days later at Wembley.