The Gunners, who will face Aston Villa in the FA Cup final later this month, are currently third in the Premier League table and the north London side have won 10 of their last 12 top-flight games.
Wenger has been linked with a move for out-of-favour Chelsea goalkeeper Petr Cech after Arsenal first-choice Wojciech Szczesny fell behind David Ospina in the pecking order at The Emirates.
Former Liverpool captain Souness believes Arsenal will need to add quality players to their squad if the Gunners want to close the gap on Chelsea and Manchester City.
Souness told Sky Sports: “Forget spine, forget any names. If you’re a big football club and you’re not strengthening, you’re standing still as all the other big teams will be strengthening. That’s a dangerous game.
“Arsenal’s group of players have certainly got better from the first part of the season until now. Can they add two or three better players in some positions? Certainly. If you asked 100 Arsenal supporters, then the answer would be unequivocal, it would be yes.”
Arsenal are two points ahead of fourth-placed Manchester United after a 1-1 draw at Old Trafford on Sunday afternoon.
United midfielder Ander Herrera broke the deadlock before Red Devils youngster Tyler Blackett put the ball past Victor Valdes in the second half.
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