LONDON—Oil was steady on Monday ahead of a meeting by OPEC and its allies which may determine whether a recent rally in prices amid supply shocks and a recovery from the COVID-19 pandemic will be sustained. Brent crude was down 6 cents or 0.1 percent at $79.22 per barrel by 0935 GMT. It rose 1.5 percent last week, its fourth weekly gain in a row. U.S. oil dropped by 13 cents or 0.2 percent to $75.75, after gaining for the past six weeks. Oil prices have risen due to the supply disruptions and a rise in global demand, pushing Brent last week above $80 to a near three-year high. “Our base case expectations for today’s OPEC meeting is that OPEC continues with its existing agreement to unwind its production cuts by around 400,000 bpd each month,” Morgan Stanley said in a note. “However if there is a reason to do …