why won't this work

Hey everyone,

Firstly what a great product AMEMBER is

I'm trying to make it so that member login on the index.php page of my site. When they login they are then taken to my directory members.
Code below
<?php
session_start();
if ($au = $_SESSION['_amember_user']){
print "Welcome $au[name_f] $au[name_l] ";
} else {
print "<form method=post action='/members/'>
username: <input type=text name=amember_login size=10>
password: <input type=password name=amember_pass size=10>
<input type=submit value='Login'>
</form>
";
}

?>

however instead of accepting the username and password it redirects the user to the custom amember login screen then back to the members section. How can I make it so it accepts the username and password on my index.php page.

I'm using new_rewrite for protection.

thanks in advance

Peter