Setting negative margin for one line

Consider the following code:

documentclass[11pt]{article}
usepackage{amsthm,amsmath}
newtheorem{thm}{Theorem}
begin{document}
begin{thm}[Locality] For two fields $A(z)$ and $B(w)$, the followings are equivalent:
    begin{itemize}
        item $A(z)$ and $B(w)$ are local, i.e. $(z-w)^N[A(z), B(w)]=0$ for large $N$.
        item $displaystyle [A(z), B(w)] = sum_{n=0}^{N-1} partial_w^{(j)} delta(z-w) gamma_n(w)$.
        item begin{align*}
        A(z)B(w) &= sum_{n=0}^{N-1} iota_{z,w} frac{1}{(z-w)^{n+1}} gamma_n(w) + :A(z)B(w): 
        (-1)^{|A||B|} B(w)A(z) &= sum_{n=0}^{N-1} iota_{w,z} frac{1}{(z-w)^{n+1}} gamma_n(w) + :A(z)B(w):.
        end{align*}
    end{itemize}
end{thm}
end{document}

The output of this code is:

I want to remove the blank line marked in red. So I tried to write down vspace{-baselineskip} before the align* environment. This gives the following weird result.

documentclass[11pt]{article}
usepackage{amsthm,amsmath}
newtheorem{thm}{Theorem}
begin{document}
begin{thm}[Locality] For two fields $A(z)$ and $B(w)$, the followings are equivalent:
    begin{itemize}
        item $A(z)$ and $B(w)$ are local, i.e. $(z-w)^N[A(z), B(w)]=0$ for large $N$.
        item $displaystyle [A(z), B(w)] = sum_{n=0}^{N-1} partial_w^{(j)} delta(z-w) gamma_n(w)$.
        item quad$begin{aligned}[t]
        A(z)B(w) &= sum_{n=0}^{N-1} iota_{z,w} frac{1}{(z-w)^{n+1}} gamma_n(w) +{} :A(z)B(w): 
        (-1)^{|A||B|} B(w)A(z) &= sum_{n=0}^{N-1} iota_{w,z} frac{1}{(z-w)^{n+1}} gamma_n(w) +{} :A(z)B(w):,.
        end{aligned}$
    end{itemize}
end{thm}
end{document}