Obama backs Ban Ki-moon for new term as UN chief

US President Barack Obama supports UN secretary-general Ban Ki-moon's bid for a second term and believes he has made important reforms at an institution that is imperfect, the White House said on Tuesday.

Obama's backing will be a valuable boost to Ban, 66, in his drive for a second five-year term, which he looks almost certain to win.

"Under Ban's leadership, the United Nations has played a critical role in responding to crises and challenges across the globe," White House spokesman Jay Carney said in a statement.

Carney cited UN efforts to support democratic transitions in Ivory Coast and earthquake-hit Haiti, a referendum on South Sudan's self-determination and efforts to resolve the political and humanitarian crisis in Libya.

"The United Nations is an imperfect but indispensable institution," Carney said. "The secretary-general 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."

Ban, whose first term ends on December 31, is unopposed for re-election so far.