Central clearing of derivatives seen adding risk Tue Jun 9, 2009 4:31pm EDT NEW YORK, June 9 (Reuters) - Proposals to require that all contracts in the $450 trillion derivatives market be centrally cleared could tie up valuable capital and constrain the liquidity of companies that use the contracts to hedge their businesses, derivatives users and dealers warned on Tuesday. The use of central clearinghouses is viewed as key to removing systemic risks posed by the contracts, should the failure of a large dealer spark a chain of losses globally. The issue arose after the collapse last year of Lehman...