Chinese officials are flocking abroad to answer President Xi Jinping’s call to woo foreign capital. Their pitch to investors is being met with doubt, partly due to the policies of their big boss.

That skepticism was on show at a ballroom in a four-star Singapore hotel last week, where officials from China's Inner Mongolia autonomous region promoted their rare earths sector to scores of potential investors.

One attendee questioned whether Beijing truly welcomed foreign investment in such minerals, which have become a focal point of U.S.-China tensions and subject to export controls.