WASHINGTON - US President Barack Obama backed Ban Ki-moon's bid for a second five-year term as chief of the United Nations, said the White House on Tuesday.

"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," the White House said in a statement.

The White House said under Ban's leadership, the United Nations has played a critical role in responding to crises and challenges across the globe.

It said Ban has made important reforms, such as increasing the hiring of women to senior posts and proposing reduction in the UN's budget.

Ban succeeded Kofi Annan in January 2007 for a five-year term, which ends on December 31 this year. For a successful reelection, the 66-year-old former South Korean foreign minister must, among others, have the support of all the five permanent members of the UN Security Council -- Britain, China, France, Russia and the United States.

France and China have expressed their support for Ban's bid for another term.