(IDEX Online) - Jewelry retailers in the US are insisting on declarations from manufacturers in India that they will not use rough stones from Russia."A number of units have received mails from the US buyers. They are worried over the matter," Dinesh Navadiya, regional chairman, Gem & Jewellery Export Promotion Council (GJEPC), Gujarat, told India's Economic Times.An estimated 250,000 diamond workers in Surat have been put on two weeks' unpaid leave as rough supplies are squeezed by sanctions and banking restrictions against Alrosa, which produces 90 per cent of Russia's output.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 say US clients are threatening to cease trading with them if they sell polished diamonds that originated in Russia.The Russian miner normally accounts for around 40 per cent (by volume) of the diamonds that are cut and polished in the Indian hub.