can you help me write correct sed/awk command to replace rc value from 1 to 6, but only for test1?

<abc>
    <an>test1</an>
    <nl>std</nl>
    <rc>1</rc>
</abc>
<abc>
    <an>test2</an>
    <nl>std</nl>
    <rc>3</rc>
</abc>
<abc>
    <an>test3</an>
    <nl>std</nl>
    <rc>1</rc>
</abc>

I have tried:
sed -i /<an>test1</an>/ s/<rc>1</rc>/<rc>6</rc> input.xml
but seems it has problem with new line encounters?