UPDATE 6-Oil falls as threat of immediate U.S. strike on Syria fades
* Obama wins backing for Syria strike from key Congress members
* Overall supply outages from Middle East, Africa at above 3 mln bpd
* Putin "does not rule out" approving Syria strike
* Coming up: API weekly oil stocks; 2030 GMT
LONDON, Sept 4 (Reuters) - Brent crude fell below $115 a barrel on Wednesday as the prospect of an immediate U.S. military strike on Syria faded and Russia said U.S. lawmakers had no right to approve such action.
U.S. President Barack Obama won the backing of key lawmakers in his call for limited strikes on Syria to punish President Bashar al-Assad for his suspected use of chemical weapons, but Russia said the U.S. Congress had no right to approve the use of force without approval from the U.N. Security Council.
While Syria is not a big oil producer, investors are worried that a strike by Western forces against the country could spread unrest in the Middle East and disrupt supply from the region that pumps a third of the world's crude.
Brent crude was at $114.67, down $1.01 by 1410 GMT. U.S. crude fell $1.22 to $107.32 a barrel.
"Oil prices are drifting lower as the immediacy of a U.S. strike on Syria has eased over the last several days," said Dominick Chirichella of Energy Management Institute.
"In any event, even if the U.S. does strike Syria it is likely to be very limited and not involve any ground troops or escalation. As such the unintended consequences from such an attack are also likely to be limited."
Middle East tension could also widen Brent's premium to U.S. crude <CL-LCO1=R> to more than $10 a barrel, from $7.32 now.
Investment bank Goldman Sachs says a limited strike would push up crude, but argues that Brent is unlikely to exceed $125.
"Brent prices above a level of around $125 are unsustainable in our view, as OECD strategic petroleum reserves (SPR) act as significant spare capacity," said the bank's analysts, led by Jeffrey Currie.
"We believe (the recent price rise) mostly reflects the events in Syria and less the increasing fundamental tightness driven by significant supply shortfalls in both Iraq and Libya, which further skews the risk to the upside."
Markets are already coping with a supply loss from OPEC producer Libya as strikes at ports and pipelines have shrunk exports to around 80,000 barrels per day (bpd), less than a tenth of capacity.
Outages from the Middle East and Africa have risen above 3 million bpd, some 3.5 percent of global demand.
Sudan's decision to lift a threat to block oil exports from South Sudan provided some relief, although Juba's output at 200,000 bpd remained lower than before the conflict shut its entire production.
The pressure on OPEC's spare capacity could peak in September on lower exports from Libya and Iraq, coinciding with a likely drop in total OECD petroleum inventories to their lowest since mid-2004, said Goldman Sachs.
Oil supply has become as tight as when the International Energy Agency ordered a rare release of strategic oil reserves during Libya's civil war in 2011, raising talks of possible action from the OECD energy watchdog.
U.S. commercial crude oil and gasoline inventories likely fell last week, a preliminary Reuters poll showed.
(Additional reporting by Florence Tan in Singapore; editing by Keiron Henderson and James Jukwey)