The Saudi-led coalition said on Monday that its forces would cease fighting for seven days, beginning on Tuesday, in order to “create the atmosphere for the success” of the negotiations in Geneva, according to a statement carried by the official Saudi news agency. Past cease-fires during the war have been marred by violations and frequently led to an escalation of the fighting.

Both the Islamic State and Al Qaeda have profited from a security vacuum while trying to rally Yemen’s Sunnis against the Shiite-led rebels, known as the Houthis, who are from the north, analysts say. Crucially, the groups have both faced little or no resistance from the Saudi-led coalition and its allies, which are focused on defeating the Houthis. The coalition receives backing from the United States and Britain.

This month, Qaeda militants were able to capture two towns in southern Yemen with little effort, residents said. In some cities, including Aden and Taiz, small numbers of hard-line Sunni militants continue to fight alongside the Saudis and their allies.

At the same time, Yemeni officials with the government of President Abdu Rabbu Mansour Hadi, which is backed by the Saudi-led coalition, have appeared to underestimate the threat posed by the Islamic State — or even deny its existence.

Last week, when the Islamic State claimed responsibility for killing the provincial governor of Aden and eight of his bodyguards with a car bomb — releasing both a statement and photographs of the attack — the city’s security director, Mohamed Mousaed, insisted that “remnants of the Houthis and Saleh” had carried out the bombing. Yemen’s former president Ali Abdullah Saleh is allied with the rebels.

Nadwa al-Dawsari, a Yemeni analyst and nonresident fellow at the Project on Middle East Democracy in Washington, said there was a widespread perception in southern Yemen that the threat from the Islamic State was “manufactured.” That perception was fueled by the group’s “invisibility,” as well as Mr. Saleh’s well-documented history of manipulating extremist groups for his own ends, including to win financial and military support from the United States for counterterrorism operations, she said.