UNITED NATIONS/SANAA - The United Nations’ peace envoy to Yemen, Jamal Benomar, has stepped down from his current position after he reportedly lost favour with Saudi Arabia and other Persian countries over his handling of worsening crisis in the impoverished Arab country.

The veteran Moroccan diplomat has been a special envoy to Yemen since 2012, making strenuous efforts to bring feuding Yemeni factions together.

A UN spokesman said a replacement for Benomar will be announced shortly. Reports suggest Mauritian diplomat Ismail Ould Cheikh Ahmed, who is presently overseeing UN’s Ebola mission in Ghana, could take the baton from Benomar.

“Mr Benomar has spent the past four years working closely with the Yemenis to realise their legitimate aspirations for democratic change fulfilled,” said an official statement from the UN.

“The Secretary-General greatly appreciates the tireless efforts Mr Benomar has made over the years to promote consensus and trust on a peaceful way forward in Yemen.” Western diplomats familiar with the matter told Reuters that the Arab nations - which are currently participating in the Saudi-led military campaign against Shia Houthi rebels in Yemen – have been increasingly frustrated over what is seen as Benomar’s soft approach towards the Houthis.

The diplomats have, nevertheless, expressed strong support for Benomar’s efforts to resolve the Yemen crisis over the last few weeks. His departure has come shortly after the UN Security Council adopted a Jordan-sponsored resolution imposing an arms embargo and a travel ban on key Houthi figures.

Meanwhile, a Saudi-led coalition pressed its air war against the Iran-backed rebels into a fourth week, promising “no half measures” in its campaign to restore President Abedrabbo Mansour Hadi. Hadi’s newly appointed Vice President Khaled Bahah called on those army units on Thursday to drop their support for the Huthis. “I call on all troops and security force personnel to accept the command of the legitimate government and protect the country,” he told reporters in Riyadh, where he is exiled along with the president.

As the air campaign entered its fourth week, Saudi Arabia’s ambassador to the United States vowed that it would continue until all its objectives were achieved. “There can be no half measures,” Adel al-Jubeir told reporters in Washington.

Jubeir said the first three weeks had been “very successful” and had “been able to degrade and destroy much of the military infrastructure that Huthis and Saleh possess.”

Coalition spokesman Brigadier General Ahmed al-Assiri said the bombing campaign had “in a large proportion” succeeded in halting the rebels’ advance in the south. Troops and militia loyal to Hadi have been battling the rebels in Aden and other southern provinces. Overnight, coalition aircraft carried out fresh air strikes on rebel positions in Aden, killing at least eight rebels, a military source said.

The World Health Organization says at least 736 people have died in the conflict since April 12 and more than 2,700 have been wounded.

The United Nations said nearly half the casualties were civilians, and UN human rights chief Zeid Ra’ad Al Hussein called Tuesday for an investigation.

Vice President Khaled Bahah said that he hoped a Saudi-led Arab coalition battling Iranian-allied Houthi rebels in Yemen would not send in ground troops.

Arab military exercises planned for Saudi Arabia have raised speculation that the coalition, which has been bombing the Houthis from the air for three weeks, is considering land operations.

“We still hope that there is no ground campaign in line with the air strikes,” Bahah told a news conference in the Saudi capital Riyadh. He called on the armed forces to support the “legitimate” Yemeni government in exile and said a ceasefire must precede any peace initiative. “At this historic moment, we send our call to all the sons of the armed and security forces to act on behalf of the legitimate state,” said Bahah.

Army units loyal to former president Ali Abdullah Saleh have joined forces with Houthi rebels against supporters of the government and forced it to flee.