Saudi Arabia, Russia, Qatar and Venezuela said Tuesday they wouldn’t increase crude-oil output above January’s levels as long as other major oil producers followed suit, people familiar with the matter said. The agreement was reached among the countries’ oil ministers at a meeting in Doha. The ministers are trying to stabilize oil prices that have plunged to their lowest levels in more than a decade as supplies outstrip demand. The decision will be communicated to other members of the Organization of the Petroleum Exporting Countries soon, officials said. Venezuela’s oil minister will meet with oil ministers from Iraq and Iran, which have both been increasing production, in Tehran on Wednesday.