LONDON—Oil rose towards $84 a barrel on Tuesday, within sight of a three-year high, supported by a rebound in global demand that is contributing to energy shortages in big economies such as China. With demand growing as economies recover from pandemic lows, the Organization of the Petroleum Exporting Countries (OPEC) and allied producers, collectively known as OPEC+, are sticking to plans to restore output gradually rather than boost supply quickly. “OPEC+ will push ahead with its cautious approach to supply in the year-end period. Set against this backdrop, oil bears will remain in hibernation mode,” said Stephen Brennock of oil broker PVM. Brent crude was up 17 cents, or 0.2 percent, at $83.82 a barrel by 1000 GMT. On Monday it reached $84.60, the highest since October 2018. U.S. oil gained 8 cents, or 0.1 percent, to $80.60, having hit its highest since late 2014 on Monday at $82.18. Jeffrey …