'These are the things I want for you -- to grow up in a world with no limits on your dreams and no achievements beyond your reach, and to grow into compassionate, committed women who will help build that world,' Obama wrote in his letter, published in the latest issue of Parade magazine.
'I want every child to have the same chances to learn and dream and grow and thrive that you girls have. That's why I've taken our family on this great adventure,' Obama said in the letter addressed to Malia and Sasha.
Feeling sorry that in the last two years he did not get enough opportunity to spend time with them because of the presidential election campaign, Obama says: 'I am so proud of both of you. I love you more than you can ever know. And I am grateful every day for your patience, poise, grace, and humour as we prepare to start our new life together in the White House.'
Obama writes: 'I know how much I've missed these past two years, and today I want to tell you a little more about why I decided to take our family on this journey.'
Observing that like any other young man, he also wanted to be successful and get the things he wanted, Obama said all this changed after fatherhood.
'Suddenly, all my big plans for myself didn't seem so important anymore. I soon found that the greatest joy in my life was the joy I saw in yours,' he wrote.
'And I realised that my own life wouldn't count for much unless I was able to ensure that you had every opportunity for happiness and fulfillment in yours,' Obama wrote.
'In the end, girls, that's why I ran for president: because of what I want for you and for every child in this nation,' Obama wrote.
Obama said he wanted all children to go to schools worthy of their potential, schools that challenge them, inspire them, and instill in them a sense of wonder about the world around them.
'I want them to have the chance to go to college -- even if their parents aren't rich. And I want them to get good jobs: jobs that pay well and give them benefits like healthcare, jobs that let them spend time with their own kids and retire with dignity,' he said.
The father said he wants to push human boundaries to reach beyond the divides of race and region, gender and religion that keep people from seeing the best in each other.
In an apparent reference to the two wars in Iraq and Afghanistan, Obama said: 'Sometime we have to send our young men and women into war and other dangerous situations to protect our country, but when we do, I want to make sure that it is only for a very good reason, that we try our best to settle our differences with others peacefully, and that we do everything possible to keep our servicemen and women safe.'