Five OPEC oil ministers will meet their counterparts from independent oil-producing countries April 26 in efforts to stabilize sagging oil prices, the Organization of Petroleum Exporting Countries reported. An employee of OPEC's information secretariat said Monday both the meeting with non-OPEC countries and a subsequent extraordinary meeting of oil ministers from all 13 OPEC countries will take place at the group's headquarters. The second meeting will take place on April 28. Each session was originally planned for three days earlier. No reason was given Monday for the change. After five OPEC oil ministers met here on April 9, OPEC President Rilwanu Lukman, who is also Nigeria's oil minister, announced the upcoming talks to consider halting an oil price slide. Lukman and the oil ministers of Saudi Arabia, Algeria, Venezuela and Indonesia have invited at least seven non-OPEC oil producing nations to meet them on April 26. Big producers such as the Soviet Union, Britain and Norway are unlikely to be represented. According to the Nicosia, Cyprus,-based Middle East Economic Survey, an influential weekly specializing in oil, the seven nations were Mexico, Oman, Egypt, China, Colombia, Malaysia and Angola.