The UN has announced its special envoy to Yemen is stepping down after four years of efforts to reach a peaceful political transition in the Arab world’s poorest country, The Guardian reported Thursday.

A statement on Wednesday night said Jamal Benomar “has expressed an interest in moving on to another assignment” and that his successor will be named “in due course”.

Benomar had come under criticism from some Middle East countries, particularly Saudi Arabia, as his efforts to broker peace showed little success.

A Saudi-led coalition has carried out weeks of air strikes in an attempt to push back Shia Houthi rebels who swept south from their region near the Saudi border and caused the president to flee.

The UN said it would “spare no efforts to relaunch the peace process”.

The pressure on Benomar, a Moroccan diplomat, had grown as the Houthis grew bolder in recent weeks. By late last week, Saudi Arabia’s ambassador to the UN was strongly hinting that Benomar was on the way out.