The extra 2,500 seats -- released once the safety application has been completed -- takes West Ham's home above Emirates Stadium's 60,260 and just behind the Tottenham Hotspur Stadium's maximum of 62,850.
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"Everyone here is doing everything we can to grow and develop this football club, on and off the pitch, for the benefit of our supporters, and we all feel that things are moving in the right direction," West Ham manager David Moyes said.
"The supporters being back has been fantastic and the atmosphere they have created, with 60,000 in the stadium, has been right up there every game.
"Having more fans in here cheering the team on will make it even better for us all and we are really looking forward to welcoming more of our young supporters and families to London Stadium."
When contacted by ESPN, the club said they were exploring the best configuration of the additional seating and are hopeful of implementing the increase by next season at the latest. Their ultimate aim is to move to 67,000 in the future following enhancements to the Bobby Moore and Sir Trevor Brooking Stands.
West Ham United Vice-Chairman Baroness Karren Brady said: "The application to increase the matchday capacity will give an even greater number of our fans the opportunity to watch our exciting team in action in person.
"Since the regular return of supporters this year, we have seen a terrific response with every Premier League fixture so far this season sold out, and we thank them for their continued fantastic backing including breaking attendance records as part of regular capacity crowds at London Stadium. This is another great sign of progression during a hugely-positive time for the club."