Ariel Helwani says that UFC 249 will likely take place on the West Coast of the United States but admits Dana White and the UFC are keeping the exact location a secret. (1:31)

UFC 249 has a new headliner.

With Khabib Nurmagomedov in Russia and facing potential travel issues, Tony Ferguson will now meet Justin Gaethje in the main event of UFC 249 on April 18, UFC president Dana White tweeted Monday. The fight for the interim lightweight title is "signed" and "100%" on, White wrote.

The fight is signed and is 100% ON LIVE on ESPN somewhere on EARTH!!!! 😃@TonyFergusonXT vs @Justin_Gaethje is LIVE on @espn+ PPV April 18th for the interim lightweight belt! pic.twitter.com/aH44zg5K30 — danawhite (@danawhite) April 6, 2020

The location of UFC 249 remains undisclosed. White tweeted that the fight will be "somewhere on EARTH!" ESPN's Ariel Helwani reported Sunday night that the UFC is targeting a venue on the West Coast for the card. It will more than likely take place in front of no fans.

White later said in an interview with ESPN he has had the card "locked up for two months" and that he was "going to continue to pump fights out."

"I've also secured an island. I've got an island," White told ESPN. "The infrastructure is being built right now. We're going to do all of our international fights on this island. When we do this fight on April 18, international and U.S., we're going to start cranking. The UFC will be back up and running internationally and the U.S."

Gaethje tweeted on Monday: "#forthepeople I'm terrified and I f---en love it. #ufc."

The UFC 249 main event (available starting at 10 p.m. ET on April 18 on pay-per-view through ESPN+, with the preliminaries on ESPN starting at 8 p.m.) was supposed to be held in Brooklyn with Nurmagomedov defending his lightweight title against top contender Ferguson. However, the coronavirus pandemic has forced the UFC to change its plans. New York has become the epicenter of COVID-19 in the United States and all large gatherings in the state -- and many other places around the world -- have been canceled.

Several of the bouts officially announced for the card, including the co-main event between Rose Namajunas and Jessica Andrade, were scheduled to take place on the original UFC 249 event. Others, such as the high-profile bout between Francis Ngannou (14-3) and Jairzinho Rozenstruik (10-0) were pulled from other cards entirely. That fight was originally supposed to headline UFC Fight Night on March 28 in Columbus, Ohio, and is now a blockbuster addition to the UFC 249 lineup. And others, a welterweight contest involving Vicente Luque and Niko Price for example, are new fights that combine two athletes originally scheduled to compete on the postponed cards, but against new opponents.

Meanwhile, White's quest to hold a UFC fight while virtually all high-level sports competition have stopped hit an obstacle later Monday when the Association of Ringside Physicians issued a statement calling for the indefinite suspension of all combat sports events.

"Any combat sport taking place during this global pandemic places the athletes, officials, and anyone else involved in the event under unnecessary risk of infection and transmission of COVID-19," ARP's statement read. "In addition, combat sports athletes often require medical attention after a bout, and we do not wish to see any additional strain on an already overwhelmed medical system."

To hold an event, White will have to find ringside physicians willing to work against the ARP's recommendation. The UFC already is likely to be forced to hire its own judges and referees while serving as its own regulatory body, since most state athletic commissions will not currently allow an event to take place in their jurisdictions.

Most UFC fighters have expressed an eagerness to fight during the pandemic. Mixed martial artists typically don't get paid unless they fight, although Bellator and other promotions have paid fighters whose bouts were canceled by the pandemic in recent weeks.

Nurmagomedov flew home to Dagestan late last month with a location for the bout still unknown. The undefeated champ told ESPN's Brett Okamoto last week that he would still fight Ferguson if he knew the location of the bout and could get there. White tweeted Sunday that Nurmagomedov was out of the event.

Ferguson, who lives and trains in Southern California, is currently ranked No. 2 in the world at lightweight by ESPN. Gaethje, who lives and trains in Colorado, is ranked No. 4. Both are considered among the most exciting fighters in the world at any weight class.

Ferguson (25-3) has won 12 straight and has not lost since 2012. He is coming off three consecutive finishes against a murderers' row of top lightweights: Donald Cerrone, Anthony Pettis and Kevin Lee. Ferguson, 36, holds the longest winning streak in UFC lightweight history, yet has never gotten a shot at an undisputed title. Five times now fights between him and Nurmagomedov have been booked and fallen through.

Gaethje (21-2) has won three straight finishes over Cerrone, Edson Barboza and James Vick. The Arizona native has won $50,000 fight-night bonuses for either fight of the night or performance of the night in all six of his UFC fights. Gaethje, 31, is the former World Series of Fighting lightweight champion. One of the best action fighters in the sport and nicknamed "The Highlight," Gaethje has gone to decision only twice in 23 career fights.

Information from The Associated Press contributed to this report.