Lionel Messi wants to stay at Barcelona, but it is "never easy" to renew his contract, according to the club's technical secretary Eric Abidal.

Messi's future has been thrown into doubt following a turbulent week at Camp Nou, during which he criticised Abidal in a social media post for his comments on the squad's efforts under former coach Ernesto Valverde.

The Barca captain called on Abidal to name names and accused him of "dirtying" the squad by suggesting certain stars downed tools during Valverde's final weeks in charge.

With Messi able to have his contract cancelled at the end of the season and leave for free, there have been suggestions he could seek a new challenge for 2020-21, although Pep Guardiola insisted on Friday he did not want Manchester City to sign the Argentina star.

Abidal seems hopeful of extending Messi's contract, which will expire in June 2021, but he concedes it is difficult to negotiate terms with a player considered the greatest in the world.

"It's a question for him," he told Mundo Deportivo when asked about Messi's contract. "Hopefully, he continues.

"Leo said Barca is everything for him, that he wants to continue here and, from there, there are conditions. We're talking about the best player in the world and to have a renewal of such a player is never easy."

Messi has always seemed likely to end at least his European career with Barca, although it is said he wants the club to be in a strong position to challenge for LaLiga and the Champions League before he commits to new terms.

Abidal appears hugely confident in Barca's chances of continental glory this season, suggesting they could be unbeatable if they play to their highest level.

"The Champions League is the objective. We know the challenge is difficult but it's not impossible," he said, with Napoli up next in the round of 16.

"For me, Barca's only rivals are Barca. If the team is good physically and mentally, it will be very difficult for us to lose the ball and not be able to win."

Barcelona's trophy hopes have already been dealt a blow by the loss of Luis Suarez, who is not likely to return until near the end of the season due to a knee injury.

The striker will also be out of contract after next season, but Abidal expects to begin discussions over a new deal when the time is right.

"First, you have to have respect for the players, for what they're giving, what they've given before and what they will give to the club," he said. "It's an injury situation now. Hopefully, he'll recover well and, aside from that, it's just talking.

"If things look good to us as a club, of course we'll enter into negotiations and he will also have to tell us how he feels because, in the end, it's [about] respect for the club and for the team."