Current and threatened U.S.-China tariffs could slash global economic output by 0.5% in 2020, the International Monetary Fund warned on Wednesday as world finance leaders prepare to meet in Japan this weekend.

IMF Managing Director Christine Lagarde said in a blog and briefing note for G20 finance ministers and central bank governors that taxing all trade between the two countries, as President Donald Trump has threatened, would cause some $455 billion in gross domestic product to evaporate — a loss larger than G20 member South Africa’s economy.

“These are self-inflicted wounds that must be avoided,” Lagarde said in an IMF blog post. “How? By removing the recently implemented trade barriers and by avoiding further barriers in whatever form.”