President Donald Trump told Chinese President Xi Jinping that direct or indirect Chinese assistance to Iran was totally unacceptable, U.S. Ambassador to China David Perdue said. Perdue said Beijing assured Washington on Thursday that it would not continue helping Tehran and that the United States had already observed some movement, although he did not specify the measures involved. An Iranian senior official disputed that account, telling Reuters that Chinese officials had assured Tehran that Beijing would not restrict its economic, political or military relationship with Iran because of Trump’s pressure. The dispute follows reports that China supplied Iran with shoulder-fired air-defense systems and helped it circumvent U.S. sanctions on oil exports through barter-like arrangements for Chinese goods. U.S. lawmakers had urged Trump to confront Xi over allegations that Chinese entities assisted Iran in ways that may have contributed to attacks causing U.S. casualties.