SANAA, Yemen — Attempts to ease fighting in Yemen appeared to falter Thursday, as Shiite rebels pressed an offensive in the south and a Saudi Arabia-led coalition intensified its airstrikes less than two days after it said it was scaling back the campaign.

All sides have declared their willingness to enter talks, but none has taken any steps to end the conflict that has killed more than 1,000 people.

Still, the head of U.N. operations in Yemen said in an interview with The Associated Press that a renewal of such talks is “inevitable,” and behind-the-scenes diplomatic efforts could bring results in the coming weeks.

The battle in the Arab world’s poorest country pits the Iranian-backed rebels known as Houthis and their allies — military units loyal to former President Ali Abdullah Saleh — against the Saudi-led coalition and the forces of President Abed Rabbo Mansour Hadi. Although Hadi is the internationally recognized leader, he was forced to flee his southern stronghold of Aden last month as the Houthis advanced toward the port. He is in the Saudi capital of Riyadh.