Felix made the big announcement on her official Twitter feed: “Decided to go for the double (200/400) at WC’s. Will be very difficult, but first step to accomplishing greatness is trying.”

Felix recently won the 400 title at the U.S. championships in June in Eugene, Ore., becoming the first woman to win national titles in the 100, 200, and 400 over a career.

Felix will be among the headliners on the U.S. worlds team heading to South Korea, a squad that also includes national champions David Oliver (110 hurdles), Lashinda Demus (400 hurdles), Derek Miles (pole vault), Matthew Centrowitz and Morgan Uceny (1,500 meters), Kara Patterson (javelin), Jessica Cosby (hammer throw), Marquise Goodwin (long jump) and William Nelson (steeplechase).