SUNDERLAND have suffered a double transfer blow after moves for defensive duo Virgil van Dijk and Carl Jenkinson both hit a major stumbling block.

Celtic assistant manager John Collins has revealed that van Dijk will not be sold until Celtic have tackled the qualifying rounds of the Champions League, while West Ham have signalled their intention to offer Jenkinson a second loan spell at Upton Park.

Van Dijk is Dick Advocaat’s leading defensive target, with the Black Cats head coach determined to land the Dutch centre-half despite Celtic holding out for a fee of around £10m.

Sunderland officials had been hoping to begin negotiations with their counterparts at Parkhead next week, but while van Dijk is still expected to leave the SPL before the transfer window closes at the start of September, he will not be going anywhere until Celtic have attempted to qualify for the group stages of the Champions League.

The Scottish champions are due to enter the Champions League at the second qualifying round stage, with matches planned for July 14-15 and 21-22, and will also face a two-legged third round tie in August if they come through their opening two matches unscathed.

“Virgil van Dijk is staying, certainly for the Champions League qualifiers,” said Collins. “He has two years left on his contract.

“Everyone connected with Celtic loves Virgil. He’s a great player and we want him to remain in a Celtic jersey this season. He is such an important and commanding player for us. He stops goals going in at one end and scores them at the other, so we want to keep him.”

With Celtic interested in signing Steven Fletcher, Sunderland could use the Scotland international as leverage in their discussions over van Dijk.

Celtic have also been linked with Watford forward Ikechi Anya, and Collins admits he is an admirer of both attackers.

“They (Fletcher and Anya) are two players I like,” he said. “But they are Premier League players and everyone knows what the salaries are like in the Premier League. That said though, we would maybe like another couple of players to come in before the start of the season.”

As well as pursuing van Dijk, Sunderland are also hoping to sign Jenkinson on a season-long loan from Arsenal.

They have agreed a loan fee of £1.5m for the full-back, who is currently on international duty with England Under-21s at the European Championships, but Jenkinson has expressed a desire to remain in London.

That option is now open to him after West Ham co-chairman David Gold signalled his desire to re-sign the 23-year-old, who was on loan at Upton Park last season, and while Sunderland remain in a strong position after reaching an agreement with Arsenal, they could find it difficult to lure the defender to the North-East.

“We know we need a right-back and we will work tirelessly to bring in Carl,” said Gold. “If that does not work out, we have other irons in the fire.”

With a midfielder also on their agenda, Sunderland are tracking Jordy Clasie, with the Holland international expected to leave Feyenoord this summer.

Feyenoord anticipate losing the £10m-rated midfielder before the transfer window closes, and have already lined up Vitesse Arnhem’s Marko Vejinovic as his likeliest replacement.

Advocaat is well aware of Clasie’s talents, and Sunderland have joined Southampton and Italian side Roma in pursuit of the 23-year-old, who would add some much-needed creativity to the Black Cats midfield.