Jquery :: Changing Background Position On Mouse Hover?

I tried to create a mouse over effect using jquery. When user hovers #box1_trigger link, the #service_box1 div should change it's background position. The code I created is the following it's not working for some reason.

html:
<div class="service_box box1" id="service_box1">
<a href="#" id="box1_trigger">
<h3> </h3>
<p> </p>
</a>
</div>

javascript:
<script type="text/javascript">
$(document).ready(function() {
$("#box1_trigger").hover(
function() {
$("#service_box1").stop().animate({backgroundPosition:"(0 -250px)"}, "slow");
},
function() {
$("#service_box1").stop().animate({backgroundPosition: "0 0"}, "slow");
}
);
});
</script>

css:
#service_box1{
width:318px; height:282px;
float:left;
background:url(images/services_panel.png) 0 0 no-repeat;
}
a#box1_trigger{
width:100%; height:100%;
float:left;
display:block;
}