UNITED NATIONS- Both sides in the conflict in Yemen have largely stuck to a ceasefire agreed last month, but substantial progress would be needed before more talks can be held on ending the war, the UN special representative to the country said on Wednesday.Martin Griffiths told the United Nations Security Council he had met the leaders of both sides in the conflict in recent days and both had expressed determination to find a way forward."I am pleased to report that both sides have largely adhered to the ceasefire we agreed in Stockholm," Griffiths said. "There has been a significant decrease in hostilities since then."He said while there had been some violence, it had been remarkably limited compared with in the lead-up to Stockholm.However, while there was a sense of tangible hope and optimism, there was also concern, Griffiths said, adding that he and the leaders of both parties shared the view that "substantial progress, particularly on Hodeidah, is something we would like to see before we reconvene the next consultations.""I am still hopeful that we can proceed to a next round of consultations within the near future and I am working with both parties to make sure that that will happen at the earliest possible date," he said.