Functional C++11 strange behavior

Why this line doesn't compile:

function<const int&(const int&, const int&)> min_ptr = min<int>;

But this works fine:

const int &(*min_ptr)(const int&, const int&) = min<int>;

It would seem that function class is flexible and comfortable replacement for function pointers. But why this case doesn't work?

EDIT. My code:

#include <functional>
#include <algorithm>
#include <cmath>
using namespace std;
int main()
{
    const int&(*min_ptr)(const int&, const int&) = min<int>; //It is works fine
    function<const int&(const int &, const int&)> min_f = min<int>;// Doesn't compile
    /*
       Error message:
        error: conversion from ‘<unresolved overloaded function type>’ to non-scalar type 
        ‘std::function<const int&(const int&, const int&)>’ requested function<const int&(const int &, const int&)> min_f = min<int>;
    */
    return 0;
}