On March 27, China signed an agreement to invest $400 billion in Iran over the next 25 years in exchange for a continuous supply of Iranian oil. The text of the agreement was not made public. An earlier, leaked draft of the deal specified that China would invest in Iran's ports, railways, and banking, healthcare, information technology, and telecommunications industries. In exchange, according to two unnamed Iranian sources—an official and an oil trader—Iran would provide oil to China at a substantial discount. The draft also called for Chinese-Iranian military cooperation in weapons development, joint exercises, research, and intelligence-sharing. Chinese Foreign Minister Wang Yi and Iranian Foreign Minister Javad Zarif signed the agreement during Wang's visit to Tehran, where Wang also met with Iranian President Hassan Rouhani. The deal had been under negotiation since 2016, when Chinese President Xi Jinping proposed it during a visit to Tehran. Iranian Supreme Leader Ayatollah Ali Khamenei accelerated talks with China after the United States re-imposed economic sanctions on Iran in 2018.