As Donald Trump sets to take oath as the 45th President of the United States, outgoing President Barack Obama shared an emotional farewell letter on the social networking site Facebook.

Expressing his gratitude to the US people, Obama wrote on Thursday: "Throughout these eight years, you have been the source of goodness, resilience and hope from which I've pulled strength. I've seen neighbours and communities take care of each other during the worst economic crisis of our lifetimes."

Obama recalled the Charleston Church shooting and said that he had mourned with grieving families searching for answers.

Obama noted that he had watched scientists help wounded war heroes walk again and seen "scientists help a paralysed man regain his sense of touch".

The outgoing President recalled some positive points of his tenure like providing access to healthcare and legalising same-sex marriages

.

"I have seen the youngest of children remind us through their actions and through their generosity of our obligations to care for refugees, or work for peace, and, above all, to look out for each other," Obama further wrote.

"When the arc of progress seems slow, remember: America is not the project of any one person. The single-most powerful word in our democracy is the word 'We'. 'We the People'. 'We shall overcome'."

"I'll be right there with you every step of the way," he added.

The 44th US President shared a link on his Facebook post for anyone interested in keeping in touch with his work.