WORLD oil prices trekked sideways near new highs on Monday as dealers contemplated the possibility of further gains in the approach to the northern hemisphere winter. Benchmark Brent crude in London slipped 16 cents to $22,28 in some mild profit taking from a peak of $23,50 on Friday, the highest oil price since January 1997. Further assurances from Opec that it will not tamper with supply curbs when ministers meet next week helped contain the losses. Opec’s tough line on exports has more than doubled oil prices since February carrying Brent within reach of a $25 post-Gulf War peak.