(IDEX Online) - Diamond sanctions are beginning to bite in India, as US buyers demand guarantees that polished stones were not mined in Russia, according to news reports.The US outlawed rough, gem-quality diamonds shortly after the invasion of Ukraine in February, but the ban does not cover stones that are "substantially transformed" - namely cut and polished - elsewhere.However, manufacturers in Surat say US clients are threatening to cease trading with them if they sell polished diamonds that originated in Russia.Indian diamond trader Naimesh Pachhigar told New Indian Express: "The US government has issued a circular to local American traders asking them to check the origin of diamonds before buying or selling them."The circular states that if the origin of the diamonds is Russia, then don't accept them."He said all traders in the country had been hit by rough shortages since the war.Dinesh Navadiya, Gujarat region chairman of the GJEPC (Gem Jewellery Export Promotion Council) said: "American buyers have refused to buy finished diamonds that started as raw ones mined in Russia."