* Dollar flat ahead of Fed meeting on Wednesday
* Pound unchanged by Brexit extension to Jan 31. 2020
* Swiss franc weakens, Australian and Canadian dollars rally
* Graphic: World FX rates in 2019 tmsnrt.rs/2egbfVh (Updates prices, adds Swiss franc, Canadian dollar, Tusk)
By Elizabeth Howcroft
Oct 28 (Reuters) - The Swiss franc weakened broadly against its rivals on Monday, extending its week-long losing streak, while the Australian and Canadian dollars gained as hopes of a Sino-American trade deal encouraged a move away from perceived safe-haven assets.
In a further sign of improving risk appetite, the Canadian dollar, a barometer of sentiment towards global trade, strengthened to a three-month high versus the greenback .
"Positive trade headlines continue to support our view that trade tensions are easing," said Win Thin, global head of FX strategy at Brown Brothers Harriman.
"We believe there is a high probability of some trade deal being signed next month, including lowering of existing tariffs."
The franc's weakness, though broad-based, was most pronounced against the trade-oriented currencies such as the Australian dollar, against which it fell 0.3% to a near five-month high.
The greenback was on the back foot on Monday after notching up a 0.5% rise last week news on Saturday that the U.S. and China are "close to finalizing" some parts of a trade agreement.
It was down 0.1% on Monday at 97.76.
In another sign of waning dollar bullishness, speculators cut their long-held long dollar positions against a broad basket of its rivals including some emerging market currencies to $15.31 billion as of Oct. 22, versus $20.79 billion the previous week, according to calculations by Reuters and the U.S. Commodity Futures Trading Commission.
This is the smallest long position since Sept. 17.
Investors are focused on the U.S. Federal Reserve meeting on Wednesday, when policymakers are expected to cut interest rates - a move which is already priced in though Fed watchers will be waiting for clues on the future policy outlook.
"There's still an awful lot of discrepancy and uncertainty in the markets as to what the Fed will do next year," said Jane Foley, senior FX strategist at Rabobank, adding that "the market will be looking for clues as to which way that might go".
MUFG currency analyst Lee Hardman expects October's rate cut to be the last one for 2019.
The euro was broadly firmer, up 0.1% against the dollar and 0.2% against the yen, while the pound was unchanged after European Council President Donald Tusk's announcement that EU leaders agreed to accept the UK's request for a Brexit extension until Jan. 31 2020.
"The outlook for the euro has improved along with expectations for a trade deal and a Brexit deal," Foley said, noting that a Brexit deal would be not only good for both the UK and eurozone economy.
In a busy week for central banks, investors will also watch the Bank of Japan's policy decision on Thursday, which is expected to be a close call on whether to unleash more stimulus or hold fire for now.
Reporting by Elizabeth Howcroft; Editing by Giles Elgood and Timothy Heritage