The safe-haven yen and Swiss franc rallied against the dollar on Tuesday as risk appetite eased after US President Donald Trump said a trade deal with China might have to wait until after the 2020 US presidential election.

China's offshore yuan fell to its weakest versus the dollar since October after Trump's comments.

The surprise statement hit the US dollar broadly as investors dumped the currency, which has tended to rise when optimism over a trade deal has grown. Market participants have long been waiting for a final trade deal, especially as both countries appeared to be nearing a preliminary one.

Trump said he had no deadline on agreement with Beijing, sparking a selloff in equities.

The news came after Trump on Monday said his administration would impose tariffs on metal imports from Argentina and Brazil on Monday and likely would impose more on a range of French goods.

"Markets have been jostled around with Trump's newfound affinity for trade tariffs," said Mazen Issa, senior FX strategist at TD Securities in New York.

"In the last 24 hours, he has ignited tensions with Brazil, Argentina, France and China. Nonetheless, risk sentiment has absorbed the latest developments," he added.

In mid-morning trading, the dollar fell 0.3% against the yen to 108.60 yen. Against the Swiss franc, the dollar also slid, down 0.4% at 0.98752 franc.

The dollar index slipped 0.1% overall to 97.743 China's offshore yuan was a big casualty as well, with the with the dollar rising 0.4 percent to 7.0695 yuan, its highest since late October.