The US Energy Information Administration has trimmed its forecasts of OPEC's net oil export earnings to $1.011 trillion this year and $1.105 trillion in 2012, down $17 billion and $3 billion respectively.
In July, the EIA forecast that the oil producer group's net earnings would total $1.028 trillion in 2011 and $1.108 trillion in 2012.
The figures are based on projections from the EIA's latest Short-Term Energy Outlook, which was published last week.
The EIA, statistics arm of the US Department of Energy, pegged OPEC's net oil export revenues last year at $778 billion in nominal terms, up 35% from 2009. Saudi Arabia earned some $225 billion in 2010, 29% of the OPEC total, the EIA estimated.
OPEC last month released its annual statistical bulletin in which it reported a $160 billion year-on-year increase in its oil export earnings to $745 billion last year from $585.3 billion in 2009, although earnings were still well below the $996.9 billion recorded for 2008 when oil prices soared to all-time highs of more than $147/barrel.
Data published in the oil producer group's Annual Statistic Bulletin showed that OPEC kingpin Saudi Arabia boosted its export earnings to $196.2 billion from $157.4 billion the previous year, an increase of almost $39 billion.
Only Qatar's 2010 earnings were higher than those of 2008. The Gulf emirate's 2010 oil export earnings came in at $29.3 billion, up from $28.2 billion in 2008. OPEC's figures include refined products as well as crude.
Oil prices have spent much of this year at elevated levels, supported to a large extent by the loss of Libyan crude supplies, with North Sea Brent crude trading at a two-and-a-half-year high of $127.02/barrel on April 11.
But gloomy economic forecasts have helped drive oil prices down in recent weeks. On August 9, ICE Brent futures traded below $100/b for the first time since February and NYMEX light crude futures traded below $80/b for the first time since late last year.
At 1009 GMT, ICE Brent traded at $108.96/b and NYMEX crude at $86.96/b.
