International benchmark Brent futures reversed lower in American trade after earlier gains in Europe, amid mounting concerns over weaker global demand next year, with some analysts believing OPEC's output cuts not enough to balance the market.
As of 13:30 GMT, Brent fell to $60.75 a barrel, with a session-high at $62.31, and a low at $60.55.
Brent rose 2.4% on Friday, the second profit in three days, marking two-week highs at $63.68.
OPEC announced on Friday a deal with Russia and other producers to cut output by 1.2 million bpd starting next January.
OPEC will cut 800 thousand bpd from its end while independent producers will cut 400 thousand bpd.
Russia alone pledged to cut 228 thousand bpd from October levels numbered at 11.41 million bpd.
Investment bank Morgan Stanley noted that current cuts might not by enough to balance the market in the first half of 2019.
As global economic growth, and oil demand in turn, slow down, OPEC might be forced to conduct largest output cuts to achieve desired balance.