(Update 1: Wed 10/09/14 20:54:54)

LONDON (Sept 10): Top oil exporter Saudi Arabia told OPEC that it reduced its oil output in August by 400,000 barrels per day (bpd), a cutback coinciding with a drop in oil prices towards the kingdom's preferred level of $100 a barrel.

In a monthly report issued on Wednesday, the Organization of the Petroleum Exporting Countries said Saudi Arabia reported August production of 9.597 million bpd, down from 10.005 million bpd in July.

A steady drop in oil prices, which for Brent crude fell below $100 on Monday for the first time in 14 months, has raised the question of whether Saudi Arabia, holder of the world's largest spare output capacity, will curb its output.

Riyadh, supported by Kuwait and the United Arab Emirates, has boosted supply informally to cover for unplanned outages in other OPEC members in recent months including in Libya, which is now seeing its production recover.

While Saudi has reported lower production in August, some analysts noted its output often falls when domestic demand for air conditioning declines from its summer peak and lower production does not necessarily mean lower exports.

"I think we can be pretty sure the Saudis are cutting," said Samuel Ciszuk, analyst at the Swedish energy agency. "But maybe the crude burning has come down a bit and I'm sceptical that they have reduced exports by as much as 400,000 bpd."

So far, OPEC has not expressed concern about the drop in crude prices, seeing it as temporary. Kuwait's OPEC governor said on Wednesday she expected prices to rise again and maintain the $100-a-barrel level.

OPEC also publishes production figures from secondary sources, a legacy of past OPEC disagreements about countries' reported output figures. According to these, Saudi Arabia cut output by 55,000 bpd to 9.86 million bpd in August but overall OPEC output rose to 30.35 million bpd, due to recovery in Libya and higher exports from Angola.

In the report, OPEC cut its 2014 global oil demand growth forecast for a third consecutive month and also reduced its assessment of the requirement for its members' crude oil.

OPEC now expects oil demand to rise this year by 1.05 million bpd, down 50,000 bpd from the previous estimate. Demand will grow a little faster in 2015, but OPEC trimmed the estimate by 20,000 bpd.

The report reduced the forecast demand for OPEC crude in 2014 and 2015 by 160,000 bpd in each year to 29.45 million bpd and 29.20 million bpd respectively, citing the lower demand forecast and a higher expectation of non-OPEC supply.

Rising supply from outside OPEC, in particular the United States due to its shale energy boom, has put OPEC's market share under pressure.

U.S. crude production averaged 8.6 million bpd in August, the highest since 1986, the government's Energy Information Administration reported on Tuesday.

OPEC's next meeting to review output policy is in November. The meetings have become less of a focus for traders in recent years as they have not changed the group's official output target of 30 million bpd.