NEW : Geithner emphasizes expanding trade and investment . OBAMA : China says its large imports of Iranian oil have nothing to do with Tehran 's nuclear program . Officials also talk about improving economic ties between China and the United States .
NEW : Geithner emphasizes expanding trade and investment . Discussions are expected to cover tensions over possible sanctions on Iranian oil exports . China says its large imports of Iranian oil have nothing to do with Tehran 's nuclear program . Officials also talk about improving economic ties between China and the United States .