Jan 18 (Reuters) - Rio Tinto on Tuesday reported a 5.4% drop in its fourth-quarter iron ore shipments, hit by a delay in completion of a new greenfield mine in Western Australia and lower demand from top consumer China as it looks to cut carbon emissions.

The world's biggest iron ore producer shipped 84.1 million tonnes (Mt) of the commodity in the three months to Dec. 31, down from 88.9 Mt a year earlier. It slightly beat a UBS estimate of 84 Mt. (Reporting by Sameer Manekar and Harish Sridharan in Bengaluru; Editing by David Gregorio)