WASHINGTON - Yemen has recently experienced some of the fiercest fighting yet in its war between the Saudi-led coalition and Houthi rebels supported by forces loyal to former President Ali Abdullah Saleh.

Repeated violations of a U.N.-sponsored cease-fire have made it impossible to resume talks that were set to take place in mid-January.

William Rugh, a former U.S. ambassador to the United Arab Emirates, said the cease-fire had not been adhered to because "the Saudis can’t so far accept a cease-fire that doesn’t give them at least the appearance of a victory, and the Houthis can’t accept a cease-fire when they still control so much of the country.”

U.N. Secretary-General Ban Ki-moon has reiterated his deep concern about the continued conflict and has called on all warring parties to commit to peace talks facilitated by the U.N.

Rugh said the U.N. has tried since the middle of last year to broker a settlement but has not been able to persuade the warring parties to negotiate seriously. He thinks the U.S. has limited leverage over the warring parties and recommends an outside, neutral mediator as a first step.

“I would think the Omanis have the best chance of playing that role, but outside mediation is not enough," he said. "The parties have to be willing to agree to a cease-fire and to accept the terms of the mediation.”

The veteran diplomat said a protracted conflict would only aggravate the mounting number of civilian casualties and worsen the already alarming humanitarian crisis in Yemen.

The continued hostilities in Yemen make it a dangerous place not only for civilians but also for journalists. VOA freelance reporter Almigdad Mojalli, killed in a Saudi-led coalition airstrike this month, was the latest journalist to die in the conflict.

Islamist militants have also launched a spate of deadly attacks on Yemeni government and security targets.

On Thursday, Islamic State militants claimed responsibility for a suicide car bombing outside President Abdu Rabu Mansour Hadi's residence in Aden that killed at least six people.

Officials said Hadi, the country's internationally recognized leader who is backed militarily by the Saudi-led coalition, was inside his residence at the Maashiq Palace at the time of the attack but was unharmed.

Hadi's office, in a statement carried by the government-run Saba news agency, said 11 other people were also injured in the attack, in which a car tried to crash through a security checkpoint guarding the palace.

In a statement posted online, IS said the attack was carried out by a suicide bomber it identified as Abu Hanifa al-Hollandi. The nom de guerre suggested the attacker was a Dutch citizen.