ALGIERS, Oct 21 (Reuters) - Algeria posted a trade deficit of $10.33 billion for the first nine months of 2015, against a $4.09 billion surplus a year earlier, after a sharp fall in energy earnings caused by the drop in crude oil prices, official data showed on Wednesday.

The deficit pushed down the coverage of imports by exports to 74 percent, from 109 percent in the January-September period of 2014, according to customs figures.

Oil and gas exports, which accounted for 94.6 percent of total sales abroad, were $27.29 billion for the first nine months of the year, down 41.4 percent year on year.

The value of overall exports in the period dropped by 40.2 percent year on year to $28.86 billion, while imports fell 11.3 percent to $39.19 billion.

Algeria has been trying to reduce its import bill in the face of the oil price slump, which it expects to cut energy earnings by 50 percent this year.

(Reporting by Hamid Ould Ahmed; Editing by David Goodman) ((;))