West Ham are close to a £25m deal for Chelsea defender Kurt Zouma.
Head coach David Moyes was desperate to bolster the Hammers before their return to European competition.
Zuma, 26, has medical treatment and it is understood that personal terms have been agreed, with the deal nearing completion.
“We received an offer that was accepted by Chelsea for Kurt but I haven’t been able to tell you if the medical examination has been completed yet,” Moyes said.
The France defender played 36 games for Chelsea last season but Thomas Tuchel is not seen as a long-term prospect, who has been targeting Sevilla’s French defender Jules Conde.
The head of the Blues also confirmed that the deal is imminent.
“There are negotiations between West Ham and Chelsea over Kurt,” Tuchel said.
“Kurt is not with us now but not because of these negotiations. He had some personal and family issues and we allowed him to travel to France.
“There are negotiations but frankly I don’t know where that leads us now.”
Zuma joined Chelsea at the age of 19 from Saint-Etienne In January 2014 he spent loan spells in the Premier League with Stoke and Everton.
He made 151 appearances for the Blues in all competitions, scoring 10 goals.
West Ham started the season in style, scoring consecutive wins against Newcastle and Leicester To top the English Premier League After two games.
However, Moyes knows he needs more players if West Ham are to maintain their lead once the competing demands in the Premier League and Europa League begin to take hold next month.