"It's definitely going to be a Great Day in South Carolina!"
Later on Wednesday, Sen. Tim Scott, R-S.C., announced through his office he will soon deliver remarks in South Carolina and Iowa, both of which are key states in the presidential primary cycle.
Pence, Haley, Scott and other possible 2024 GOP contenders are also set to speak at an Austin, Texas, conference on Feb. 24, the Texas Tribune reported earlier Wednesday.
With his rivals looking more likely than ever to challenge his perch atop the GOP, Trump has taken some newer, harder swipes on social media.
Trump said over the weekend that he had spoken to Haley on the phone and encouraged her to run.