West Ham have warned fans against racist behaviour when the Hammers play Tottenham on Monday.
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The match, where the 20th anniversary of Bobby Moore's death will be marked, comes three months after anti-Semitic chanting marred the reverse fixture.
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Hammers chairmen David Gold and David Sullivan issued a statement on Friday.
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"We must be clear that we will pursue the harshest sanctions against any individual who goes against what we stand for as a club," they said.
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Two West Ham fans accepted a police caution, and one of them was given a lifetime ban from matches for gestures made at the 25 November match which Spurs won 3-1.
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The two cautioned supporters are understood to have made Nazi-style salutes aimed at Tottenham supporters, who traditionally have strong ties with London's Jewish community.
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Hammers manager Sam Allardyce said: "I hope there's nothing untoward that happens in terms of chanting.
the fans should learn to behave themeselves in football matches
maybe fifa need to set up rules for the fans too