Arthur Melo's proposed move from Gremio to Barcelona might not be as imminent as expected with Sport now claiming that a last minute interest from Manchester United and Monaco could delay the negotiations.

Yet, the Spanish publication says that the La Liga leaders remain optimistic of winning the race as the negotiations are on track, with only minor details to sort out.

Chelsea, United [Daily Mail] and even Real Madrid [Marca] have been linked with the 21-year-old in recent months but Barcelona emerged as the main candidates to secure his services since after the player was photographed in a Blaugrana shirt alongside club technical secretary Robert Fernandez.

Barcelona can not register Arthur now as Ernesto Valverde already has the maximum number of non-EU players in the form of Philippe Coutinho, Yerry Mina and Paulinho but they have been trying to secure a deal as soon as possible in order to avoid a big summer battle for his services.

Earlier this week, Mundo Deportivo reported that Barcelona technical secretary Fernandez arrived in Brazil on Saturday [17 February] to step up the negotiations and later Sport announced that the clubs had reached an agreement in principle over a deal which could rise to €40m (£35.4m, $49.3m) with add-ons.

Sport said that Arthur has a €50m release clause in his contract but Barcelona would pay €30m plus €10m extra in variables after agreeing to keep the promising midfielder at Gremio until the January transfer window of 2019.

The move appeared to be just a mere formality after Sport added that Arthur was expected to undergo his medical on Wednesday (21 February) in what it looked like the last step before completing the proposed move.

Nevertheless, the Spanish publication said that personal terms between Arthur and Barcelona were agreed weeks ago and Fernandez was only expected to reaffirm those terms.

But now Sport themselves have revealed a new chapter in the saga by claiming that Monaco and United could still launch a last minute ditch attempt to hijack the deal.

The Spanish publication says that the Ligue 1 side have already launched a €22m offer to sign him.

The bid is much lower that the one made by Barcelona but Sport says that there will be a big commission involved and they will offer Arthur the chance of moving to Europe as early as this summer.

Meanwhile, United are yet to make a bid but Sport understand that Jose Mourinho is keen on the signing and would be ready to pay more than Barcelona to acquire his services.

One way or another Sport suggests that the interest from both clubs will only serve to delay the deal with Barcelona remaining optimistic they can complete the move.

But for the moment the report suggested the medical originally scheduled for Wednesday has been delayed, with a new date yet to be identified even with talks at an advanced stage.