U.S. Ambassador to the United Nations sent this email to her staff at the U.S. mission this morning:

Dear Colleagues and Friends,

As you have likely now heard, this afternoon President Obama announced that he is appointing me his next National Security Advisor. I am deeply honored and excited to continue to serve our country in this new capacity.

But, in truth, I am very sad to leave the work and the people of the US Mission to the UN. Serving with you at USUN has been the best job I have ever had – challenging, fun, multifaceted and never, ever dull. The greatest part, however, has truly been the people. Every morning, no matter how tough or arcane the issue, I have awakened with a bounce in my step because I knew that whatever was coming at us, I would have the privilege of confronting it with the best team of people I have ever worked with. Your dedication, commitment, kindness, good humor and excellence have been unfailing.

So, above all, I am deeply grateful to each of you – from the UPOs whose smiling faces lift my spirits when I walk in the building to each officer and OMS, each driver, advisor and Ambassador, each DS agent, each military staff committee member, each IMO. Every single one of you has given me your best. It has been my greatest privilege to serve alongside you, the remarkable public servants at the lean and mean U.S. Mission to the UN.

I could not be prouder of you and of all that we have accomplished together. As a team, we have strengthened America’s relationships and advanced U.S. interests and values at the United Nations. None of this would have been possible without your professionalism and commitment.

I will begin to make this transition shortly, but my last day at USUN will be at the end of June. I am very excited that President Obama has nominated Samantha Power to be my successor. If confirmed, you all will love working with her, as many of you have already discovered. She is wicked smart, energetic, strong, principled and a truly lot of fun.

In the meantime, I am confident that USUN will continue to excel in all areas of the mission’s work, under the extremely able leadership of Ambassadors DiCarlo, DeLaurentis, Cousens and Torsella. I know I will leave the mission in excellent hands, and there will be a great deal of continuity.

I look forward to seeing you all and being able to thank you in person next week. I plan to honor you all at a Happy Hour in the near future.

I will greatly miss the USUN family. You are the best!

Susan