* U.S. threat of 25 pct tariff on $200 bln in Chinese goods-source
* Yuan falls; Aussie dollar down 0.3 pct
* Dollar broad strength keeps euro, yen in check
* Graphic: World FX rates in 2018 http://tmsnrt.rs/2egbfVh
By Tommy Wilkes
LONDON, Aug 1 (Reuters) - The dollar strengthened on Wednesday, sending the Chinese yuan towards recent lows and pressuring the Australian dollar on fears of an imminent escalation in the trade dispute between the United States and China.
A source familiar with the matter said the Trump administration plans to propose a 25 percent tariff on $200 billion in Chinese imports, up from an original 10 percent, in a bid to pressure Beijing into making trade concessions.
With a possible escalation in the months-long dispute and fears about what it would mean for the Chinese and then the global economy, investors bought into the dollar and sold currencies linked to China's economic fortunes.
The greenback rose 0.2 percent against a basket of currencies before pulling back, while against the offshore yuan gained more than half a percent to as high as 6.8458 yuan , not far from the recent peak of 6.8562.
The news came as a survey showed China's factory sector grew at the slowest pace in eight months in July as export orders declined yet again.
The yuan has now fallen for four months in a row and China's central bank on Wednesday set the currency at its weakest since May last year.
The Aussie dollar, seen as a proxy for Chinese growth because of Australia's big export sectors, slipped 0.3 percent while a sidelined euro was down 0.1 percent at $1.1682.
Still, analysts said the reaction of currency markets was limited, in part because Trump's latest batch of proposed tariffs were expected and in part because the trade tensions are yet to have an impact on economic data.
"The markets have calmed down relatively quickly Maybe the market is underestimating the economic impact of the tariffs and that is why it is keeping calm," said Thu Lan Nguyen, an FX strategist at Commerzbank in Frankfurt.
This week also sees a number of central banks meeting, with the U.S. Federal Reserve due to conclude its policy meeting later in the day and the Bank of England holding its event on policy meeting on Thursday.
The Bank of Japan held its meeting on Tuesday.
Against the yen the dollar rose 0.2 percent to 112.10 as Tuesday's pledge by the BoJ to keep rates extremely low for an extended period continued to weigh on the Japanese currency.
"Relative to other major central banks, the BoJ is now decisively the last cab off the easy policy rank," said Ray Attrill, head of FX strategy at National Australia Bank.