SHANGHAI - President Barack Obama is telling Chinese students that the United States will always work to push for its core values of freedom of expression and political participation.

Obama on Monday opened a town hall-style meeting in Shanghai with a vow to call out other nations who ignore the principles important to the United States. Obama said his country struggled with slavery and unequal rights for women and minority groups were difficult, but overcame those institutions because the nation embraced the principles of its founding.

He says the United States doesn't want to impose a form of government on other nations but would also not remain silent.

Obama's opening statement straddled praise for Chinese traditions and strong words for a key trading partner.