Trying to make a simple click counter

Python code:

button = 0

def button_up(btn):
    btn = btn + 1
    return (btn)


import tkinter as tk
root = tk.Tk()
root.title("Click Game!")
root.maxsize(300,300)
root.minsize(300,300)


button1 = tk.Button(root, text="Click me!", command=button_up(button))
button1.pack()

label1 = tk.Label(root, text="Click Counter: ")
label1.pack()

label2 = tk.Label(root, text=str(button))
label2.pack()