The secretive government agency that supervises China’s foreign exchange reserves used its funds to help convince Costa Rica to sever ties with Taiwan and establish relations with Beijing last year, according to documents obtained by the Financial Times.

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Full list of SAFE’s financial holdings in UK-listed companies

The purchase of US-denominated Costa Rican government bonds by China’s State Administration of Foreign Exchange (Safe) is the clearest proof yet that Beijing regards its $1,800bn in foreign reserves – the world’s biggest – as a tool to advance its foreign policy goals, as well as a potential source of income.