Relations between the United States and the United Nations have sometimes been rocky.
Various US governments have threatened to cut its funding or even have it moved out of its headquarters in New York.
But the US is still the biggest financial backer of the agency.
Now, US President Donald Trump's administration is rejecting the UN's nominee - Salam Fayyad - for the role of peace envoy to Libya.
Fayyad is a former Palestinian prime minister.
The UN says he would be serving in a personal capacity, and not as a representative of any government.
But Nikki Haley, the new US ambassador to the UN, is moving to block his appointment.
She says Trump's administration is "very disappointed" at his selection for this role because in her words, to "the detriment of Israel'.
So, are these signs of a growing rift between a superpower and an organisation meant to bring the world together?
Presenter: Sami Zeidan
Mouin Rabbani - Former head of political affairs at the Office of the UN Special Envoy for Syria.
Ambassador Mokhtar Lamani - Former Arab League and UN diplomat.
Scottie Nell Hughes - Chief political correspondent for USA Radio Network.
Source: Al Jazeera News