Mediators have achieved progress in efforts to get the United States and Iran back to negotiations and avert an all-out war in the Middle East, two regional officials said Monday, with a pause in attacks coming after a period of rapidly escalating tensions.

The comments came after neither the U.S. nor Iran reported carrying out any attacks for three straight days — a respite after about two weeks of sustained bombardments that had led to increasing fears of a return to all-out war.