Nurmagomedov is the undisputed lightweight champion, while Poirier is the interim champ. UFC 242 is scheduled for Sept. 7 in Abu Dhabi.
Nurmagomedov (27-0) has established himself as one of the top fighters in the world. The 30-year-old Russian last fought at UFC 229 last October, beating Conor McGregor in the fourth round via submission.
The Nevada State Athletic Commission suspended the Dagestan, Russia, native for nine months after a post-fight scrum with McGregor and members of his team. White said that a rematch between the two hasn't been ruled out.
"We'll sit back and watch how this whole thing plays out with these fights, and see where Conor fits in and what he wants to do next," White said. "I absolutely could [see a rematch]. Conor wants that fight. Conor wants the rematch with Khabib."
Poirier (25-5, 1 NC) is riding a six-fight win streak. He won the interim title after beating Max Holloway at UFC 236 in April. The Louisiana native has a 9-1 record, with one no contest, since moving up to the lightweight division in 2015 after losing to McGregor.
Ali Abdelaziz, the manager of Nurmagomedov, told ESPN that his client inked a new multi-fight deal with the UFC before the bout against Poirier was announced by White on Tuesday. Terms of the agreement weren't disclosed.
Abdelaziz said there is specific language written in the contract if Nurmagomedov ever fights former two-weight champion Georges St-Pierre. St-Pierre is currently retired, but Nurmagomedov's team has expressed interest in a possible fight.
"We have a tall order in front of us. Dustin Poirier is a great fighter and our main focus," Abdelaziz said. "None of these other guys have a guaranteed title shot, except for Georges St-Pierre. There is a clause in the contract for that fight. If Georges comes back, we're fighting Georges and it's already been negotiated.
"This deal is so massive for Khabib, Dana White had to go back to his pawn store and sell some of the stuff back he bought there. That's how big this deal is. We're extremely happy. It's a fair deal. And one of the things Khabib is most happy about is his father will be able to corner him in Abu Dhabi."
UFC 242 will be the promotion's first fight card in Abu Dhabi since 2014.