Vice President Joe Biden headed Tuesday to China under the cloud of criticism over the US debt as he seeks to build a rapport with the rising Asian power's enigmatic next leader.

Biden flew out of Andrews Air Force Base near Washington en route to China, where he will spend an unusually long five days before visiting emerging US partner Mongolia and longtime ally Japan.

The number-two US leader's trip was months in the planning and came at the invitation of Vice President Xi Jinping, who is expected to become China's top leader by 2013 and remains virtually unknown in US policy circles.

But while Biden will focus his trip on building a working relationship with Xi, his trip risks being overshadowed by a row over China's scoldings of the United States, which this month came within hours of defaulting on its debt.

China is the largest foreign holder of US bonds. China's state-run media was scathing over the political showdown on the debt, calling the United States irresponsible and demanding that it live within its means.

Lael Brainard, the undersecretary of the Treasury for international affairs, insisted that the US economy remained the "most flexible, the most innovative" in the world and that the August 2 debt deal was a "major step" toward fiscal responsibility.;_ylv=3