Off-late oil price declines have driven the speculations higher about the USD/SAR peg's breaking possibility. This is unlikely. 12 month forwards are already setting to price in SAR weakness. 

This clearly signals that there is a doubt regarding the peg's sustainability in the markets. The general refrain from analysts is that plenty of FX reserves will prevent the breakage, but this seems not to make sense.

If Saudis have to continually intervene to maintain the peg, as FX reserves decline, which they have already started to, the remaining reserves become more precious. At a certain time, the authorities have to ask if a strategy like that is tenable.

"Given that the Saudis have to issue large amounts of debt over the coming years in order to cover their budget shortfall, any increase in speculation about a peg break means that investors might not be so willing to buy this debt", says Commerzbank in a research note. 

Moving the peg soon or later to keep track of the declines in their terms of trade is a more clever strategy and to re-confirm investors that this is more sustainable than the old one as it is more realistic in pricing levels, either of the cases investors benefit from asymmetric trade.