The Swiss National Bank set a cap of 1.20 francs to the euro which it pledged to defend with all available means. Yet the franc has been gaining ground against the euro since former SNB Chairman Philipp Hildebrand became embroiled in a currency trading scandal in late December.

Without a permanent central bank head, some in the market see the SNB as easier to take on. Yet UBS economist Reto Huenerwadel disagreed with that view.

"As one might expect under similar circumstances, the above news (of the downgrades) impacted EURCHF negatively pushing the cross ever closer towards the SNB's lower boundary of 1.20," Huenerwadel said in a note.

"However, we see few reasons to push below this critical mark," Huenerwadel added, explaining that there was no need to believe the SNB would step back from its defence of the franc despite Hildebrand's resignation last Monday following a controversial currency trade made by his wife.

The franc was also largely unchanged against the dollar, remaining within striking distance of an 11-month low struck on January 9.

The franc was little changed against the euro compared to Friday's New York close, trading at 1.2074 francs to the euro by 0816 GMT.

The franc was stable against the dollar at 0.9529 francs to the dollar.