Alaska Governor Sarah Palin is to resign this month and will not run for re-election.
Gov Palin was vice presidential running-mate to Republican presidential candidate John McCain in last year's election and rallied the party's conservative base.
There has been speculation that she would seek to be the Republican Party's presidential candidate in 2012.
'She didn't take any questions,' in making the announcement in Alaska, Andrew Wellner, a reporter for The Frontiersman, told CNN.
'She did say in her speech that she feels she can be more effective working outside of government'.
Ms Palin said her decision came after much 'prayer and consideration'.
She said she did not want to waste time on 'political blood sport' and cited public criticism of her actions and her family since the 2008 campaign.
