Oman cargoes with a 0.2 percent operational tolerance were sold at premiums of about 5 cents a barrel above the official selling price (OSP), against premiums of about 4 cents from the previous year, they said.

The rise in outright prices and higher interest rates have increased financing costs for traders when they purchase Oman on the Dubai Mercantile Exchange, the sources said.

The higher premiums for Oman were also indicative of expectations of lower supplies from Iran next year as US sanctions hit Tehran's exports, one of the sources said.

The International Energy Agency said in its monthly report on Friday that Iran's supply has dropped to a two-and-a-half year low in September.

Talks were ongoing for cargoes with a 5 percent operational tolerance, the sources said.

Some of the sources expected deals to be done at premiums of 14-15 cents a barrel although an upstream company may have sold its supplies at premiums higher than 15 cents.

For 2018, Oman cargoes with a 5 percent operational tolerance were sold at premiums of 10-12 cents.