UN Secretary-General Antonio Guterres yesterday urged the warring sides in Yemen to reach a political settlement to end a conflict now in its fourth year that has left 22 million people in urgent need of aid.

His Special Envoy Martin Griffiths will head to the United Arab Emirates, Oman and the Yemeni government-held city of Aden in the drive for peace, Guterres told reporters.

Griffiths has already held talks with both sides in the war which has drawn in regional powers, meeting Huthi authorities who hold the capital Sanaa as well as internationally-recognised Yemeni president Abd-Rabbu Mansour Hadi and Saudi officials in Riyadh.

Guterres said he saw "positive perspectives" for preparing a plan of action "to lead to an effective inter-Yemeni dialogue able to achieve a political solution, with of course the involvement of all those that are relevant in this conflict".

"I am optimistic about that possibility," the UN chief added.

Yemeni Foreign Minister Abdel-Malek al-Mekhlafi called for a return to the negotiating table and said that his government was working to open ports and airports to aid.

"We need to find the ideal solution which is a return to the talks table, to put an end the war, to return to a sustainable system supported by the people of Yemen," he said, adding that this should include "the putschist parties" - referring to the Huthis - and those supported by the international community.

Guterres also announced that more than $2 billion has been pledged towards a UN humanitarian appeal of $3 billion for Yemen this year.