Decides: (a) to call once again upon the parties concerned to implement immediately Security Council resolution 598 (1987); (b) to extend the mandate of the UN Iran-Iraq Military Observer Group for a further period of 6 months until 30 Sept. 1990; (c) to request the Secretary-General to submit, at the end of this period, a report on the developments in the situation and the measures taken to implement Security Council resolution 598 (1987).