PARIS (Reuters) - Almost 30 aid groups wrote to French President Emmanuel Macron on Monday evening threatening to shun a conference on Yemen co-chaired by Saudi Arabia, one of the warring parties, unless France as host ensured its aims were purely humanitarian, not political.

French President Emmanuel Macron walks back inside the Elysee Palace in Paris, France, June 4, 2018. REUTERS/Philippe Wojazer

France earlier confirmed that the gathering of countries and international organizations would take place on June 27 in Paris to address the “urgent humanitarian situation”.

A Saudi-led coalition backed by the West has been carrying out air strikes against the Iran-aligned Houthis since 2015 in a war to restore the internationally recognized government.

Since then, more than 10,000 people have been killed, 3 million driven from their homes and more than 8 million left severely short of food, in what the United Nations says is the world’s worst humanitarian crisis.

Coalition-backed troops have now advanced to within 10 km (6 miles) of the Red Sea port of Hodeidah, which has a population of 400,000 and handles the bulk of Yemen’s aid supplies, raising fears of a major battle that could shut the port and exacerbate the crisis.

“We are concerned about the credibility of a humanitarian event on Yemen co-hosted by Saudi Arabia, one of the parties to the conflict,” said the letter, seen by Reuters, from 27 aid groups including Oxfam, Christian Aid and the Norwegian Refugee Council.

They said they would not support the meeting unless France, as the convener, ensured “all parties to the conflict participate and engage in good faith, guided by the sole objective of alleviating the suffering of Yemenis”.

Macron has sought to position himself as a mediator in conflicts as far away as Libya and Lebanon as he looks to fill a void left by the United States and other leading Western powers.

Paris provides weapons, training and intelligence to the Saudi-led coalition. Its Foreign Ministry said on Monday that the meeting, which Saudi Arabia would co-chair, would discuss the difficulties in getting aid to the population, including the situation at Hodeidah.

It is unclear how this might fit into U.N. mediator Martin Griffiths’ efforts. He said in April he wanted to present a plan for negotiations within two months to end the conflict, but that any new military offensives could “take peace off the table”.

The NGOs said a conference that did not “set down strict and clear conditions and outcomes” might only embolden the warring parties at a time when restraint was needed.