* S.Africa platinum producers, union agree 'in principle' wage offer
* Gold falls after hitting 3-week high in previous session
* Fed's two-day policy meeting begins later in the day
(Updates throughout, changes dateline from SINGAPORE)
LONDON, June 17 (Reuters) - Gold fell on Tuesday as investors withdrew money from the top bullion fund before a Federal Reserve meeting, while platinum traded flat as details had yet to emerge on a wage agreement in the South African mining sector.
Anglo American Platinum, Impala Platinum, Lonmin and union AMCU have agreed on a wage deal to end a five-month strike, but the timeframe and additional benefits are unresolved, a spokesman for Impala Platinum said.
Spot platinum was down 0.2 percent at $1,426.30 an ounce by 1024 GMT. The metal gained just 4.6 percent throughout the strike, reflecting an abundance of above-ground stocks, analysts said.
"Despite some headlines little seems to have changed in the strike dynamics since Thursday, but that in itself is putting pressure on the platinum price given it suggests a resolution remains near," Macquarie analyst Matthew Turner said.
Spot gold fell 0.4 percent to $1,266.00 an ounce, retreating from a three-week high of $1,284.85 hit on Monday, when turmoil in Iraq and Ukraine supported its safe-haven appeal relative to higher-risk assets such as equities.
"When gold is driven by geopolitical news, there's a tendency that this has to keep getting worse for gold to improve," Turner said. "If news stabilises, gold tends to fall back."
Militants have routed Baghdad's army and seized the north of the country in the past week, threatening to dismember Iraq and unleash all-out sectarian warfare with no regard for national borders.
U.S. and Iranian officials discussed the crisis in Iraq on the sidelines of separate negotiations about the Iranian nuclear programme in Vienna.
"Market participants no longer appear to rate the geopolitical risks quite as highly as before, meaning that gold is in less demand as a safe haven," Commerzbank said in a note.
"Presumably it has been financial investors above all who have taken advantage of the latest increase in the gold price to grab profits while they can."
Gold investors were also monitoring the Fed meeting, which is seen as bearish for the metal due to prospects for a slightly hawkish outcome, Macquarie's Turner said.
The Fed's two-day policy meeting begins later in the day, with a statement expected on Wednesday. Markets are on the watch for any signals on when the U.S. central bank might begin raising interest rates.
Sentiment was bearish as holdings of SPDR Gold Trust, the top gold-backed exchange-traded fund, dropped 4.20 tonnes to 782.88 tonnes on Monday - near a five-year low.
The decline is the biggest outflow since mid-April.
Among other precious metals, silver was unchanged at $19.60 an ounce, while palladium was down 0.1 percent at $807.50 an ounce.
(Additional reporting by A. Ananthalakshmi in Singapore; Editing by Dale Hudson)