OPEC and a group of 10 oil-producing nations led by Russia are deepening their crude production cuts, but remain split on whether the curbs should remain in place through the end of the year, officials said Sunday. Saudi Arabia, the de facto leader of the Organization of the Petroleum Exporting Countries, met with Russia and a few other countries here to review how the 24-nation coalition is complying with a December agreement to withhold 1.2 million barrels a day from global markets. …