Amir Khan's next defence of his WBA light-welterweight title will be against IBF champion Zab Judah in Las Vegas on 23 July.
The 24-year-old British fighter, who beat Paul McCloskey in April, had been linked with fights against Timothy Bradley or Erik Morales.
Khan confirmed the fight on Twitter, writing: "July 23, WBA/IBF unification fight. KHAN vs JUDAH. Mandalay Bay."
Judah, 33, reclaimed the IBF title against Kaizer Mabuza in March.
Writing on his own Twitter page, Judah said he was confident he could win the sixth world title of his career.
"Who coming to Vegas on July 23 to see me become 6x Champion of the World!!!," he tweeted.
His career includes victories over Junior Witter and Cory Spinks, while he has lost to the likes of Carlos Baldomir, Floyd Mayweather Jr and Miguel Cotto.