The rupee opened with a negative bias amid a strong dollar and rising US treasury yields and depreciated 18 paise to 96.38 against the US dollar as market sentiments continue to dampen amid simmering tensions between the US and Iran. Forex traders said rupee remains vulnerable to the rise in crude oil prices as also the closure of the Strait of Hormuz hampering its exports and imports to the Gulf countries. At the interbank foreign exchange market, the rupee opened at 96.38 against the US dollar, registering a fall of 18 paise from its previous close.