Sunderland's hopes of signing Diafra Sakho held up by West Ham's failure to strengthen attacking ranks

The Hammers are reluctant to let the Senegalese striker leave for less than £15m this summer, and are not prepared to let him go at all until they have secured a replacement.

Sunderland have learned that is unlikely to soon, with West Ham looking certain to miss out on two of their main striker targets.

Lyon indicated they are not prepared to sell Alexandre Lacazette before the start of the season and are keen to keep the Frenchman.

West Ham had made a £25m offer, prompting Allardyce to think Sakho would be an easier signing than has turned out.

But Lyon club president Jean-Michel Aulas said: "We have had a few calls, but Alexandre will stay. I think it is his desire and the coach counts on him.”

West Ham’s other main target was Belgian striker Michy Batshuayi but he is to join Chelsea this week in a £40m-plus deal from Marseille.

Now Sunderland hope West Ham are more successful in persuading Fiorentina to sell Mario Gomez.

The Black Cats have made a couple of offers for Sakho but are yet to match the £15m valuation. There have been discussions with other clubs for alternatives, with Swansea’s Bafetimbi Gomis the deal easiest to conclude rather than one for Roma’s Edin Dzeko or Wolfsburg’s Bas Dost.

The Sunderland squad will begin pre-season training this morning, without any new players signed up to join in despite plenty of talks behind the scenes.

As well as attempts to bring in a strike, Allardyce has also struggled to land centre-half James Tomkins from West Ham, who could join Crystal Palace in a £10m transfer.

Lyon’s president Aulas has confirmed there has been an ‘offer from Sunderland’ for defender Clement Grenier, while Monaco and Southampton are the favourites for another Allardyce target Djibril Sidibe of Lille.

Sunderland have been linked with a move to Twente’s goalscoring midfielder Hakim Ziyech. The Moroccan has scored 39 during his time with the Dutch club is rated at £8m.