GENEVA — U.N. Secretary-General Ban Ki-moon launched Yemen peace talks in Geneva on Monday with a call for a humanitarian truce after warplanes from a Saudi-led Arab coalition pounded the Houthi-controlled capital Sanaa overnight.

More than 2,600 people have been killed since the coalition began military operations in March to stop the Iranian-backed Houthi militia moving on Aden and to shore up embattled President Abd-Rabbu Mansour Hadi, then in the southern city.

Ban said the truce, called to mark the start of the Muslim holy month of Ramadan later this week, should last for at least two weeks to allow life-saving supplies into the country.

“Today Yemen’s very existence hangs in the balance. While the parties bicker, Yemen burns,” he told reporters.

However, Yemeni Foreign Minister Reyad Yassin Abdulla dismissed the possibility of any cease-fire soon.

“If they (the Houthis) are still occupying Yemen, they are still killing innocent people, if they are still destroying everything, what kind of cease-fire?” Abdulla said in Geneva.

But he said his exiled government might consider a “limited” truce if the Houthis agreed to withdraw from cities, including Aden and Taiz, and free more than 6,000 prisoners.

Representatives of Hadi’s government were in Geneva for the talks, but a plane carrying delegates from Sanaa, including the Houthis’ Ansarullah group, had to land in Djibouti after what Yemeni political sources said was Egypt’s refusal to give the plane overflight rights.

The Houthi group’s spokesman criticized the United Nations for failing to prevent what he said was a “clear obstruction and a reckless attempt” to block delegates from reaching the talks.

Mohammed Abdel-Salam said on Facebook that the team had left for Geneva after Oman intervened to “secure the path of the plane” and he asked the United Nations to condemn “behavior that seeks to obstruct its efforts to convene political consultations.”

Oman, which remains neutral in the conflict, hosted talks between the Houthis and the United States that paved the way for the Geneva meeting.

Seif al-Washli, an adviser to the Houthi team, told Reuters in Geneva, “It is clear this was a result of Saudi pressure on Egypt and Sudan to block the delegation and humiliate them.”

Egyptian civil aviation officials denied Cairo had any objections to the Houthi delegation using its airspace.

The Geneva talks were expected to last two to three days, with the U.N. special envoy for Yemen, Ismail Ould Cheikh Ahmed, shuttling between the delegations.

Analysts said there was little sign that either the Houthis and their ally, former Yemeni President Ali Abdullah Saleh, or Hadi, now based in Riyadh, were ready to compromise.

Saudi Arabia, echoing the Hadi government, said the Geneva talks should focus on implementing a U.N. Security Council resolution demanding that the Houthis leave cities they have seized since last year.

Ban also called for the withdrawal of armed forces from the cities, saying the fighting was bolstering Islamist militants.

“The region simply cannot sustain another open wound like Syria and Libya,” Ban said.

While Western countries have largely backed the air campaign as a way of pushing the Houthis to the negotiating table, they have more recently started to press Saudi Arabia to agree to a humanitarian pause to allow aid in and to negotiate.

The crisis began when the Shiite Muslim Houthis seized Sanaa last September, saying they wanted to end corruption and discrimination. Hadi fled to Aden in February and then to Saudi Arabia as Houthi forces closed in on the southern port city.

Although the conflict is rooted in local rivalries, it has also become part of a wider regional struggle between Sunni Muslim Saudi Arabia and Shiite Iran.

Iran’s deputy foreign minister for Middle East affairs will discuss the conflict Tuesday at a meeting of the pan-Islamic Organization of Islamic Cooperation hosted by Saudi Arabia in Jeddah, the Iranian Mehr news agency reported.

The crisis has forced the United States to withdraw its military personnel from Yemen, seen by Washington as a frontline in its war against Islamist militants.

Fighting raged throughout Yemen’s south and center Monday, in clashes pitting tribesmen and pro-Hadi militiamen against the Houthis and their army allies.

Airstrikes hit Houthi positions in Saana and in the nearby province of al-Dhalea to back up local armed fighters, who exchanged heavy artillery salvos with the Houthis.

A humanitarian crisis has worsened due to an air and sea blockade imposed to stop arms supplies to the Houthis but which also cut off many citizens’ access to food, medicine and fuel.

More than 3,000 cases of dengue fever have been recorded in five provinces since the conflict began, with three confirmed deaths, the World Health Organization said.

Medical sources in Aden say dozens have died from the illness, which has spread from piles of uncollected rubbish in intense summer heat.