Is there a result allowing to seperate two connected components

Let $X$ be a subset of $\mathbb{R}^n$ such that$$X = A \cup B,$$with $A\cap B = \emptyset$ and $A$ and $B$ are two connected non empty subsets of $\mathbb{R}^n$. Is there a result allowing to prove that there exists a smooth function $F$ such that $A \subset \{x \in \mathbb{R}^n\mid F(x)<0\}$ and $B\subset \{x \in \mathbb{R}^n\mid F(x)>0\}$?