Futures gain after oil prices rise

Crude prices were hovering slightly above $30 a barrel on hopes that OPEC and non-OPEC producers would agree to tackle a massive supply glut. Chinese shares tumbled, dragging down global stocks, after a steep fall in rail freight in the world's second largest economy raised concerns about a China-led global slowdown. The Federal Reserve's Federal Open Market Committee begins a two-day meeting on interest rates later on Tuesday, its first since raising rates in December, with a statement due on W