MIDDLESBROUGH are prepared to do everything they can to prevent Marten de Roon from leaving this summer after it emerged Manchester United are the latest Premier League club to be showing an interest in him.

It is unclear where Jose Mourinho, who is looking to improve his midfield options this summer, ranks de Roon on his list of targets, but such claims are the latest sign of an ever-increasing interest in the Holland international.

Mourinho has publicly admitted before that he likes him and will have been given positive feedback from his close friend Aitor Karanka.

The Northern Echo understands de Roon’s former club Atlanta have joined the battle for his signature too, after qualifying for the Europa League and armed with greater spending power after six months of player sales.

Atlanta have raised money by agreeing deal for Roberto Gagliardini, Mattia Caldara, Franck Kessie and Andrea Conti for a combined total of more than £80m this year, and that has given the Serie A club far more money than they would normally have to spend over a summer.

They had hoped that Middlesbrough, who paid £12m for him 12 months ago, would be willing to offload him for a similar amount following relegation to the Championship.

However, Middlesbrough chairman Steve Gibson has outlined his wish to push for promotion and wants to give new manager Garry Monk the best possible chance to achieve that goal.

Paying more than the £12m – which would make Middlesbrough a profit – would be much easier for Manchester United, while Everton and Watford are the two other clubs to have expressed an interest.

But Gibson will play hardball with any of the players in the Middlesbrough squad who are part of Monk’s plans and can boost the bid for promotion at the first attempt.

That will be the case with defender Ben Gibson, despite huge interest in him from the top end of the top-flight, and George Friend, who has Watford as well as Burnley and West Brom chasing his signature.

Middlesbrough, who are being linked with an interest in Bristol City’s £4m-rated Aden Flint, are far more relaxed about offloading full-back Antonio Barragan.

The 30-year-old full-back has been in Spain to finalise a move to Real Betis, just 12 months after arriving from Valencia. He started last season well but lost his way and is being allowed to leave on a season-long loan with an option to buy.

Middlesbrough’s Belgian midfielder Jullien de Sart has joined Belgian First Division side Zulte Waregem on a season-long loan too, there is also an option to buy.

De Sart spent last season on loan at Derby County. The 22-year-old said: "Francky Dury has been showing interest in me for quite some time, it's an honor to work with such a coach.

"There is a lot of quality here. Despite my young age, I have already played some top level matches. My passage in England was also very educational. I want to push my mark here and get great results with Zulte Waregem, both in the league and in the Europa League."

The Middlesbrough squad is set to return for pre-season training today when they will meet up with Monk for the first time together.

Monk has met a number of players individually after agreeing to succeed Karanka and is looking to put his own stamp on the squad he will work with as he tries to lead them to promotion.

He is taking the players for an eight day warm weather training camp in the Algarve early next month and it looks like they will be playing Chesterfield while they are there, although they have not confirmed the fixture yet.

It has been suggested it will take place in Santo Antonio on July 15, just over the border in Portugal, so it is close to where Chesterfield are training in Spain as well as where Middlesbrough will be based.