Zinc held near a three-year peak on Wednesday with supply set to tighten while aluminium dipped from multi-month highs but could turn higher again as inventories fall and demand rises.

Still, some investors question whether zinc can maintain its strength, because while inventories have fallen they remain substantial and easily available.

LME zinc prices are up 15 percent this year, gaining around half of that in July, as global exchange stocks fall and amid a dearth of new mining projects to replace the world's biggest zinc mine, Century in Australia, which is drying up.

But while zinc inventories in LME-monitored warehouses have fallen more than 20 percent since March, they remain a hefty 655,000 tonnes.

There are also no lengthy waiting times to access zinc, unlike aluminium stored in some LME-monitored warehouses where buyers have to wait for months.