Set select list option value I'm trying to set value of select list programmatically with hook form alter

I have select list with options:

$options = array(125 =&gt; 'USA');


and setting value like this

$form['field_news_rubrique']['und']['#options'] = $options


But this don't work.

if i change options like this

$options = array(0 =&gt; 'USA');


it's working

if i have multiple value in options like this :

$options = array(124=&gt; 'EN', 125 =&gt; 'USA');


it's working too
Do you want to set the value before submission or after?

Before submission:
Use $form and set the default value for the select list using the key.

After submission:
Use $form_state['values']