Tough road ahead for LME's new steel, aluminium contracts

* Trading due to start on Monday * Launch of steel rebar, steel scrap, aluminium premiums * LME lines up industry players for new contracts * Building liquidity may be slow in difficult market By Maytaal Angel and Eric Onstad LONDON, Nov 20 (Reuters) - New steel and aluminium contracts to be launched next week by the London Metal Exchange (LME) are expected to attract initial interest from customers, but building up strong liquidity in the current bear market may be challeng