Slaven Bilic has confirmed that Diafra Sakho will miss the 2017 Africa Cup of Nations with a back injury.
The 26-year-old striker is expected to be sidelined for up to eight weeks, with the tournament running from 14 January to 5 February.
Sakho had already been ruled out of action for the Hammers late last month with a thigh problem.
In a press conference, ahead of West Ham's Premier League clash with Swansea City on Boxing Day, Bilic revealed that the forward had already undergone an operation on his back.
He said: "We have a few knocks, but are expecting everyone to be fit except for Diafra Sakho, who will be out for six to eight weeks.
"He will miss the Africa Cup of Nations and it is a big blow for us."