Washington - In a birthday editorial on Thursday, US President Barack Obama described himself as a feminist and urged renewed effort to break down gender stereotypes.The father of two girls, who was raised by a single mother, penned an essay for Glamour magazine, declaring "this is an extraordinary time to be a woman."I say that not just as President but also as a feminist."Listing strides made by women, from gaining the vote to cracking open previously off-bounds careers, Obama said "the most important change may be the toughest of all - and that's changing ourselves".He said raising Sasha, 15, and Malia, 18, had opened his eyes to the pressure girls are under."You see the subtle and not-so-subtle social cues transmitted through culture. You feel the enormous pressure girls are under to look and behave and even think a certain way."We need to keep changing the attitude that raises our girls to be demure and our boys to be assertive, that criticises our daughters for speaking out and our sons for shedding a tear," he wrote.Obama turned 55 on Thursday.