  Let $\Lambda$ be a uniformly discrete set and $S$ be a compact set in $R$. We
prove that if there exists a bounded sequence of functions in Paley--Wiener
space $PW_S$, which approximates $\delta-$functions on $\Lambda$ with
$l^2-$error $d$, then measure($S$)$\geq 2\pi(1 - d^2)D^+(\Lambda)$. This
estimate is sharp for every $d$. Analogous estimate holds when the norms of
approximating functions have a moderate growth, and we find a sharp growth
restriction.
