SANAA, Yemen (AP) — Yemen’s warring sides have failed to reach an agreement to extend a nationwide cease-fire, the UN said Sunday, endangering the longest lull in fighting since the country’s bloody civil war began.

In a statement, the UN’s envoy to Yemen called on all sides to refrain from acts of provocation as the talks continue, after the deadline of October 2 for extending the agreement was missed.

The UN-backed truce initially took effect in April, and raised hopes for a longer pause in fighting as Yemen’s civil war entered its eighth year. The devastating conflict began in 2014, when the Iranian-backed Houthis seized the capital of Sanaa and much of northern Yemen and forced the government into exile. A Saudi-led coalition including the United Arab Emirates intervened in 2015 to try to restore the internationally recognised government to power.

In a statement, UN envoy for Yemen, Hans Grundberg said he “regrets that an agreement has not been reached today.” He did not call out the Houthis by name for failing to agree to his proposal but thanked the internationally recognised government for “engaging positively” in talks to extend the cease-fire. He called on leaders to continue to endeavor to reach an agreement.

“I urge them to fulfill their obligation to the Yemeni people to pursue every avenue for peace,” he said.

The foreign minister for Yemen’s internationally recognised government placed the blame for the truce ending on the Houthis. In comments made with the pan-Arab Satellite channel Al-Hadath, Ahmed Awad Bin Mubarak said that Houthis had obstructed the cease-fire and gone against the interest of the Yemeni people.

“The government made many concessions to extend the truce,” he said.

There was no immediate comment released from the Houthi rebels following the UN statement. But on Saturday, the Houthis said that discussions around the truce had reached a “dead-end,” and said that they were continuing to advocate for a full opening of the Sanaa airport, and lifting of the blockade on the key port city of Hodeida.

The Iran-backed side hosted a large military parade last month, showcasing rockets and large weaponry, drawing condemnation from observers.

In the hours leading up to the deadline, a Houthi military spokesman threatened private oil companies still working in the country to leave or their facilities would be seized. Yahia Sarea wrote on Twitter that the fossil fuels belong to the people of Yemen and could be used to pay public servants’ salaries.

April’s truce had originally established a partial opening of the Sanaa airport and the Red Sea port of Hodeida. The ensuing months have seen flights start again from the capital’s airport to Jordan and Egypt. It also called for lifting a Houthi blockade on Taiz, the country’s third largest city. But little progress has been made there, after talks aimed at reopening local roads stalled. Another sticking point is how salaries of public employees will be funded, many of whom have not been compensated for years.

Sunday’s statement came a few days after Grundberg met in Sanaa with the top leader of the Houthis, Abdel-Malek al-Houthi, and other senior officials, who have been pushing for a full opening of the airport. The envoy warned last week that the risk of return to war was a real possibility.

“Millions will now be at risk if airstrikes, ground shelling and missile attacks resume,” said Ferran Puig, country director in Yemen for the international charity Oxfam, reacting to the news of the truce expiring.

Analysts say it remains unclear if further talks could make progress, with Houthis feeling empowered and the coalition fighting them splintered by inter-alliance trouble.