US President George W. Bush faces a delicate political balancing act Thursday when he welcomes Chinese President Hu Jintao to the White House: seeking China's help to end nuclear standoffs in Iran and North Korea, while urging changes to economic, military and political policies that critics say hurt US interests. For Bush, the success of Hu's visit will be judged largely by whatever concessions Washington wins on a long list of complaints. Those include allegations that China mistreats its citizens, that an undervalued currency hampers US competition, that China's growing military strength could lead to conflict in the Taiwan Strait, and that Beijing has pursued energy deals with countries the United States sees as tyrannical. For Hu, the visit provides a chance to burnish China's image at a time when Americans are wrestling with what China's new economic and political clout means here. "Part of President Hu's challenge is also to speak to the US public," Deputy Secretary of State Robert Zoellick, a leading voice on China in the Bush administration, said in a speech this week. "China does not want to be seen as a threat; it's seeking respect."