The Dec/Jan 380-cst time-spread slipped to about $7.75 a tonne on Monday from about $8.25 a tonne on Friday, broker sources said.

Looking further ahead, however, the fuel oil market structure was firmer on Monday as expectations of tightening supplies following OPEC's announcement to curb production and amid mounting pressures on Iranian oil exports provided support, trade sources said.

The later-dated Jan/Feb 380-cst time-spread climbed to $5 per tonne on Monday from $4.25 on Friday, the brokers said.

Similarly, the January 380-cst barge crack narrowed its discount to Brent crude by about 25 cents from Friday to minus $6.55 a barrel on Monday despite higher crude prices, the brokers said.

Meanwhile, cash premiums of 380-cst fuel oil edged slightly higher on Monday, but limited buying interest for physical cargoes kept the fuel premiums near Friday's 2-1/2-month low.

In the fist week of December, intense buying interest in the Singapore window for physical cargoes of 380-cst fuel oil helped boost cash premiums of the fuel as traded volumes spiked.