* German flash PMI worse than expected in Sept
* Yen undermined by hopes for U.S.-China trade talks
* China's yuan, Aussie, make some gains
* Graphic: World FX rates in 2019 http://tmsnrt.rs/2egbfVh
LONDON, Sept 23 (Reuters) - The euro fell on Monday after German flash purchasing managers' index survey data for September was weaker than expected, raising more fears about the health of the economy.
The single currency, trading around $1.10 before the numbers were released, dropped 0.4% to as weak as $1.0972, its weakest since Sept. 12.
The survey showed that the German private sector activity shrank for the first time in 6-1/2 years in September as a manufacturing recession deepened unexpectedly and growth in the service sector lost momentum.
The dollar was boosted by the euro's decline, and its index - which measures the greenback against a basket of currencies - was last up 0.3% at 98.776.
Increasing talk of fiscal stimulus in the euro zone has raised bond yields in the region, although not all analysts see much of a boost for the single currency in the context of concerns about global trade and slowdown fears.
"We see little upside scope for EUR/USD here," MUFG analysts said in a note.
Elsewhere, foreign exchange markets were mostly quiet, though there were some signs of risk appetite as Japan's yen weakened against higher-yielding FX after talks in Washington between U.S. and Chinese trade deputies were described as "productive".
Volumes in Asia were dampened by a public holiday in Japan.
A U.S.-China trade breakthrough had seemed unlikely after President Donald Trump told reporters on Friday he was "not looking" for a partial deal, and Chinese officials then cancelled goodwill visits to U.S. farmers.
But both sides later published positive statements, with the U.S. Trade Representative's office describing the talks as "productive" and China's Commerce Ministry calling them "constructive." October's high-level talks remain on track.
The yen was last down 0.2% at 107.75 yen per dollar .
China's yuan added 0.1% to 7.112 yuan in offshore markets .
The Australian dollar rose 0.1% to $0.6772, while against the yen it rallied 0.4% and was on track for its best day since Sept. 12.
Despite the more positive tone in forex markets on Monday, investors remain nervous about the geopolitical outlook, and equity markets fell in early trading.
"I think there's still a lot of nervousness around," said Shane Oliver, chief economist at AMP Capital, citing Middle East tensions and the U.S-China trade dispute as drivers.
"These things have a habit of escalating and de-escalating and then escalating again...it is a bit finely balanced at the moment," he said.
Sterling slipped slightly to $1.2459. (Additional reporting by Tom Westbrook in Singapore; Editing by Angus MacSwan)