Manchester United are continuing talks with Gremio over teenage starlet Douglas Costa.

The Times says Sir Alex Ferguson, the United manager, wants to take Douglas on a three-week trial this summer before deciding whether to make an offer for the 18-year-old, but that request was rejected by Duda Kroeff, the Grêmio president, who has told the Barclays Premier League champions to make a straight cash bid or end their interest.

Douglas is understood to have a release clause of about £21 million in his contract, which has four years left to run, but United are prepared to pay only about a third of that figure.

"I received a phone call from someone working for Manchester United," Kroeff said. "He asked for Douglas to be released [for a trial] and said that he would not play, but that they wanted to see him in action. I said to them that this will not happen.

"Douglas is not at a stage where he would go through such a situation. He is an established player, he is not a stranger. He has no need to face tests at European clubs."