Chael Sonnen vs. Wanderlei Silva moves to May 31 as Brazil headliner

While the UFC originally targeted the grudge match as the Weidman-Belfort co-main event, the escalating feud has now been deemed worthy of a headlining slot.

While the UFC originally targeted the grudge match as the Weidman-Belfort UFC 173 co-main event, the escalating feud has now been deemed worthy of a headlining slot.

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Chael Sonnen vs. Wanderlei Silva is a matchup years in the making, and apparently anticipated enough that it's got two continents fighting over hosting it.

The matchup originally seemed a lock for the U.S. when UFC president Dana White said it would serve as a co-headliner for the upcoming middleweight title fight between Chris Weidman and Vitor Belfort, but the plan has now shifted. Instead, the heat its radiating will send it to main event status. The bout will topline a May 31 card in Brazil, the UFC announced in a post on its website on Thursday.

The bout will come one week after Weidman-Belfort. There was no host venue announced, with information likely to come shortly. The card is expected to air on FOX Sports 1.

The two are currently in Sao Paulo, where their season of TUF: Brazil is soon to wrap up taping. During recent filming, the rivals and some of their respective team members engaged in a wild brawl, White recently informed the media. The feud between them stems back to a 2010 van ride where Silva warned Sonnen about disparaging Brazil, and since then, they've had several public confrontations.

On Wednesday, Sonnen offered to fill in for an injured Rashad Evans against Daniel Cormier at UFC 170, but his offer was rebuffed by the promotion in favor of keeping him on track to fight Silva. Sonnen (28-14-1) is coming off a TKO loss at the hands of Evans.

Silva (35-12-1, 1 no contest) hasn't fought since knocking out Brian Stann last March.

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