The Swiss franc maintained gains against the dollar and the euro made over a four-day Easter break when nerves over Iran and the view that the US rate cycle was nearly over strengthened the safe-haven currency.
Early on Tuesday, the dollar traded lower at 1.2791/93 francs, compared with 1.3000/05 late on Thursday, putting it near the 1.2802 level not seen since January.
The franc was also firmer against the euro at 1.5675/77 francs, after hitting one-month highs near 1.5670 francs, compared with 1.5715/20 francs late on Thursday.
The dollar had posted sharp losses on Monday due to growing concerns that the cycle of rising US interest rates may be ending and to rising geopolitical tensions over Iran's nuclear ambitions.
Later on Tuesday, the United States is set to press other major world powers to consider what it called targeted sanctions against Iran ahead of an April 30 UN deadline for Tehran over its nuclear programme.
The franc has felt underlying support from a robust economic outlook for export-focused Switzerland, which is expected to benefit from a recovery in the surrounding eurozone.
"Economic data released in Switzerland in the first quarter of this year have, up to now, confirmed a picture of economic growth underpinned across a broad front, accompanied by continued robust foreign-trade momentum, further improvement on the labour market, with a corresponding positive impact on private consumption and growing corporate investment activity," Credit Suisse said in a recent note.