West Ham United are beginning to grow frustrated in their attempts to sign William Carvalho from Sporting Lisbon as the two clubs still remain €6 million (£5.5m) apart in their valuations for the midfielder. West Ham have offered €32m (£29.1m) for Carvalho plus €5m (£4.55m) in add-ons. Sporting are holding out for €38m (£34.6m) plus €5m in add-ons and despite extensive negotiations have not yet budged. No other club has, as yet, made a serious offer for Carvalho this summer and West Ham remain confident that a deal can be done, not least because the 25-year-old holding midfielder wants to join them. Carvalho is regarded as the final piece in the jigsaw during this transfer window by West Ham manager Slaven Bilic, with the club having already brought in Marko Arnautovic for a club-record fee of up to £24m, which will be eclipsed if the Portuguese international is signed, as well as Javier Hernandez, Joe Hart and Pablo Zabaleta. All are expected to be first-team regulars with Carvalho the holding player as Bilic re-shapes his side into a more regular 4-3-3 formation. West Ham got off to a disappointing start to the campaign, beaten heavily by Manchester United last weekend, but there is optimism that the changes they have made will significantly improve the team. They face Southampton, again away, this Saturday.