U.N. Special Envoy for Yemen Ismail Ould Cheikh Ahmed, center, leaves a meeting with the Yemeni government delegation during Yemen peace talks at the United Nations offices in Geneva on June 19. (Fabrice Coffrini/AFP/Getty Images)

Peace talks in Geneva to halt the war in Yemen ended Friday without agreement as the United Nations appealed for $1.6 billion in emergency aid to avert a humanitarian catastrophe in the Arabian Peninsula country.

Few had expected a major breakthrough between representatives of the Houthi rebels and the exiled government of President Abed Rabbo Mansour Hadi during the U.N.-sponsored talks, which began Tuesday after multiple delays. Neither side has shown much willingness to compromise in a conflict that escalated when a Saudi-led coalition launched an air war against the Houthis in March.

But diplomats had hoped the Geneva discussions would at least yield a cease-fire to address Yemen’s worsening humanitarian crisis, which has been exacerbated by a nationwide air and naval blockade imposed by the Saudi-led coalition.

Speaking Friday at a news conference in Geneva, Ismail Ould Cheikh Ahmed, the U.N. envoy to Yemen, announced the failure of the peace effort but still held out hope for a cease-fire “before any next round of talks.” He gave no indication of when the next round of talks would be, saying that any progress would require “further consultation.”

At a news conference earlier in the Swiss city, U.N. Undersecretary General for Humanitarian Affairs Stephen O’Brien warned of a “looming humanitarian catastrophe” in Yemen.

As a result of the fighting, the United Nations and aid agencies warn that the country of more than 25 million has experienced a sharp rise in hunger and disease, including a widening outbreak of dengue fever, a mosquito-borne virus that can be lethal to children.

O’Brien appealed for $1.6 billion in aid donations, saying that millions of Yemeni families “no longer have access to clean water, proper sanitation or basic health care.”

A key part of delivering aid to Yemenis is cajoling the Houthis and officials from Hadi’s government to the negotiations table, which has been difficult for diplomats. Neither side agreed to negotiate directly in the Geneva talks, during which anger flared publicly on multiple occasions. During a news conference Thursday, a woman hurled a shoe at the head of the Houthi delegation, Hamza al-Houthi, calling him a murderer. In response, he threw the shoe back at the woman.

Since March, the fighting has killed more than 2,500 people and displaced nearly a million.

In February, the rebels overthrew Hadi's government, which relocated to the Saudi capital, Riyadh.

The Houthis are Shiite Muslims. Saudi Arabia, a Sunni powerhouse, sees them as proxies of its enemy, Shiite Iran.