The US support comes a day after the South Korean announced his willingness for a second term.
"President Obama welcomes United Nations Secretary General Ban Ki-moon's announcement that he will run for a second term, and the United States supports his candidacy," White House Press Secretary, Jay Carney, said in a statement.
Under Ban's leadership, the United Nations has played a critical role in responding to crises and challenges across the globe, including most recently supporting democratic transitions in Cote d'Ivoire and earthquake-affected Haiti, the conduct of the referendum on South Sudan's self-determination, and efforts to resolve the political and humanitarian crisis in Libya, he said.
Noting that the UN is an imperfect, but indispensable institution, the White House Press Secretary said Ban has made important reforms, such as increasing the hiring of women to senior posts and proposing the deepest reduction in the UN''s budget in more than a decade.
"The United States strongly supports further efforts for reform to improve effectiveness, streamline bureaucracy, reduce costs, and update business practices to improve the United Nations' ability to meet its mandate to promote global peace and security, human rights and development," Carney said.