Taipei perceives bans as retribution for US House Speaker’s trip. Please use the sharing tools found via the share button at the top or side of articles. Copying articles to share with others is a breach of FT.com T&Cs and Copyright Policy. Email licensing@ft.com to buy additional rights. Subscribers may share up to 10 or 20 articles per month using the gift article service. More information can be found at https://www.ft.com/tour. https://www.ft.com/content/ff15198f-cdc2-48fa-bed5-4a59bebbf01a China has blocked imports from hundreds of Taiwanese food producers and temporarily suspended exports of natural sand to the country in what Taipei perceives as the opening shot in a campaign to punish it economically for a visit by US House Speaker Nancy Pelosi.