Benchmark Brent crude was trading three cents firmer at $19.40 a barrel at 1030 GMT, fully double the single digit levels struck at the turn of the year amid market oversupply.

The crude hit a fresh 20-month high of $19.95 on Friday but closed 43 cents lower on the day after speculators cashed in gains ahead of the weekend.

Sentiment remained supported by signals from the Organisation of the Petroleum Exporting Countries (Opec) that it will abide by tough output limits despite the price rally.

The agreement, implemented in March and due to last a year, was aimed at trimming global oversupplies which had pulled oil prices down to historic lows at the start of the year.

A committee of Opec ministers on Friday recommended the group keep its curbs until at least the end of March to support the market and added they want average prices to rise further.

The recommendation agreed at a meeting of Iranian, Kuwaiti and Nigerian officials in Vienna will be sent to the cartel's September 22 ministerial meeting which has power to alter the output pact.

The 1998 price slide dealt a heavy blow to the economies of oil-dependent nations, many of whom are expected to want to see prices strong for many months before output curbs are relaxed.

Oil's subsequent rally followed fresh evidence of shrinking global supplies and mounting evidence that Opec has adhered closely to supply discipline in spite of the price rally.

The accord amounting to 1.7 million barrels per day for 10 Opec members was carried out in concert with additional restraint from some non-Opec producers. One of them, Mexico, has since indicated that it forsees producers abiding by the agreement until it expires.

Opec president Youssef Yousfi was quoted on Sunday by Algerian radio as saying oil exporters should stick to the agreement until it runs out since the market balance was still fragile.