Trade tensions have taken center stage in recent weeks as Trump has increased tariffs on Chinese imports, threatened to raise tariffs on Mexican imports and removed preferential trade treatment for India. The mounting tension has prompted investors to move out of riskier assets like US stocks and into safe-havens like the yen and franc.
"Though we think the recent warning shot towards Mexico could be resolved, the road ahead on the global trade front is likely to remain challenged until the G20 later this month," wrote Mark McCormick, global head of foreign exchange strategy at TD Securities.
"This backdrop leaves us taking a sell-on-rally posture with dollar/yen."
The yen hit its strongest level against the dollar since Jan. 14, at 108.05, and was last at 108.31, roughly unchanged from the prior session, in which the yen strengthened the most against the dollar within a single day since early January.
Against a basket of six other major currencies, the dollar was lower at 97.536, though it is still up 1.4pc for the year.
The franc has risen close to levels at which the Swiss National Bank has traditionally intervened to keep the currency weak.
Against the euro it rallied more than half a percent to 1.112 francs, its strongest since July 2017, though it was last weaker at 1.118. Against the dollar it was at its strongest since April 3, with the dollar 0.36pc weaker at 0.997 francs.
"While the Swiss franc has appreciated strongly in recent weeks, much of that gain is due to the wave of risk aversion sweeping across markets and we need to see further substantial gains before the central bank has to step in," said Manuel Oliveri, a currency strategist at Credit Agricole in London.
The Swiss National Bank, which pursues a monetary policy of negative interest rates and currency intervention, has traditionally intervened when the franc has risen to around 1.10 francs per euro, but low inflation and trade tensions suggest the franc has to gain far more from current levels.
The euro was stronger on the day at $1.121, erasing some of the franc's gains, but investors remained broadly cautious on the outlook of the single currency as manufacturing data in the eurozone contracted for a fourth month in July.