Manchester City manager Pep Guardiola believes Arsenal forward Alexis Sanchez is almost at the same level as Barcelona star Lionel Messi.

City has been heavily linked with a move for Sanchez — out of contract in mid-2018 — in the off-season.

Guardiola, whose team faces Arsenal in an FA Cup semi-final on Monday (AEST), gave one of his strongest indications yet that he would love to sign the Chilean, comparing him to Messi, considered one of the greatest players of all time.

"How do big clubs improve their teams? With better players. So of course big clubs around the world are going to know his situation," he said.

"When the big, big players go to Barcelona they understand that Lionel Messi is unique.

"But Alexis is just one step below. Alexis is a fantastic player and I'm so happy how he's playing at Arsenal, especially this year scoring goals.

"Put Kevin De Bruyne with one year left on his contract and see how many teams [are interested]."

Sanchez has scored 23 goals in all competitions this season, but Arsenal is below where many think it should be, currently in seventh in the Premier League.

His stunning free-kick against Middlesbrough helped it to a win last time out and Guardiola said it was that type of magic which separated Sanchez from other players.

"It was a tight game – [his] free-kick, goal, over," the Spaniard said.

"Good players make these kind of things – the difference. He’s a player of that level."