France, Jan. 16 -- As protests and repression intensify inside Iran, Beijing finds itself under growing pressure. China's long-standing principle of non-interference is colliding with its deep economic entanglement with the Islamic Republic.

When US President Donald Trump warned that Tehran would face "serious consequences" if protesters were killed, China initially stayed silent. When it did respond, it repeated familiar positions, calling for calm, opposing outside interference and restating views it said it had "always" held.

That posture shifted on Tuesday, when Trump announced an additional 25 percent tariff on countries that continue to defy Washington's policy on Iran. The measure was to take effect "definitively" and "immediatel...