Irish-born new US Ambassador to the United Nations, Samantha Power, proudly presented her credentials to UN Secretary-General Ban Ki-moon, on Monday.

Meeting with a crush of reporters as she entered the UN, surrounded by her security and staff, Power said, "Hello everybody. I am Samantha Power. I am totally delighted to be here, so honored, so thrilled to have started work as the U.S. ambassador to the UN."

Power was born in Dublin and moved to the US when she was nine years old. She won a Pulitzer Prize for her work on genocide and caught the eye of Barack Obama when he was a U.S. senator.

She served as a special assistant to Obama and was key staffer on the National Security Council.

Speaking of Ban Ki-moon she said:

"I've worked with the secretary-general over the last few years at the White House, worked very effectively with him, and I am looking very much forward to a close working relationship now that I am up here in New York.

"As I made clear in my testimony before the senate the UN is critical to a range of U.S. interests and U.S. leadership at the UN is indispensable to make progress on those interests," she said.

"We have a lot to discuss upstairs and even more to do whether it's terrorism, it's a broader range of security concerns, mass atrocities in Syria, South Sudan, the effort to alleviate global poverty, the crackdown on civil society around the world."

"There are just so many issues where the United States and the United Nations have to work together to achieve progress," Power said.

"I feel incredibly fortunate to come to New York, to be able to sit behind the placard that says the United States."