In a new setback to Afghanistan’s troubled presidential election process, plans to resume a suspended full-ballot audit Saturday were abruptly aborted when one of the two finalists refused to participate, instead demanding more changes in the examination aimed at rooting out alleged widespread fraud in the June 14 polling.

The move embarrassed U.N. officials, who had just announced confidently that the inspection would begin immediately after three weeks of disputes and delays. It was also a potential blow to the deal brokered by Secretary of State John F. Kerry last month, in which both candidates agreed to the audit and to some form of power sharing after its results are announced.

Over the weekend, hundreds of international monitors arrived in the Afghan capital to monitor the audit. It was part of a high-profile effort to salvage a political transition with high-stakes consequences for Afghanistan’s future stability and its relations with Washington and other Western powers, which backed it through a decade of post-Taliban struggles with massive amounts of military and financial support.

Jan Kubis, head of the U.N. political mission here, declared Friday that “any delays, any uncertainties would have a major negative impact” on the country’s future. “It’s high time to complete the process . . . and inaugurate the new president,” he said.

But by mid-morning Saturday, it was clear that something was amiss. The high-security facility where thousands of ballot boxes have been collected was still nearly empty of people. Aides to one candidate, former finance minister Ashraf Ghani, arrived to start observing the audit, but no one associated with his rival, former foreign minister Abdullah Abdullah, appeared.

“They were the ones who asked for the audit, and now they’re not showing up for it,” complained Daoud Sultanzoy, a Ghani campaign aide who arrived at the Independent Election Commission compound at 7 a.m. “They know they’ve lost and they’re looking for excuses.”

But senior aides to Abdullah, who spent the day negotiating behind closed doors with U.N. officials, insisted they had legitimate grievances about the audit. They charged that it was being run by Afghan election officials who had abetted pro-Ghani fraud at the polls and that the review had not been designed rigorously enough to unearth what they called a vast, elaborate scheme to rob Abdullah of victory.

“This audit is our absolute highest priority, but at this point we feel it is not robust or credible enough to dig out the massive, sophisticated fraud that took place,” Mahmoud Saiqal, a senior campaign aide to Abdullah, said in an interview late Saturday. “This is a war for democracy, and we are going to keep fighting hard against the fraud. Otherwise this will be the end of democracy in Afghanistan.”

Kubis said Saturday that the audit would be delayed by only one more day, saying that Abdullah’s campaign had requested the extra time for “clarifications” on the audit process. He noted pointedly that both candidates had formally agreed to the audit in Kerry’s presence and added that “after today’s consultations . . . we expect that the process of the audit will continue smoothly and without any interruptions.”

Although Saiqal said that “some progress” had been made in their talks, he did not hold out much hope that the remaining issues would be solved by Sunday. Among other things, Abdullah is demanding that any post-audit power-sharing arrangement give the runner-up authority to appoint some cabinet members, governors and other officials. Ghani has said this would not be acceptable.

The contretemps is rooted in the dramatically lopsided results of two rounds of presidential polling. Abdullah won the first round in April by a narrow but solid margin; the election commission called for a runoff in June and announced afterward that Ghani had beaten him badly.

Abdullah’s team protested and produced evidence that election officials had colluded with pro-Ghani fraud. Some of his armed supporters issued veiled threats to form a parallel government by force. With the transition near collapse, the election commission chief was fired and Kerry stepped in to propose the audit and joint-governing arrangement, but disputes between the two camps arose almost immediately and the audit had to be halted three times amid bickering over how to decide whether a ballot was valid or not.

Ghani supporters claim that his surprising victory was the result of hard work and an eleventh-hour appeal to his fellow ethnic Pashtun voters, who turned out in much higher numbers the second time. Abdullah’s campaign claims it was the result of wholesale ballot stuffing that resulted in some districts having almost as many ballots as inhabitants, and they demanded a detailed audit of the entire 8 million ballots cast.

Nader Nadery, chairman of the national Free and Fair Election Association, said there had been fraud on both sides of the vote, but that Abdullah and Ghani know how much is at stake in salvaging the credibility of the election and producing a new government through a scrupulous audit and fair power-sharing plan.

“There is no other way out, and both candidates understand that, but they have different interpretations in how it should work,” Nadery said. “My main worry is that the technical process will break down and no outcome will be decided. This will turn a transition into a political deal, we will go back to the old ways, and all the investment in a real democratic process will be lost.”

As of late Saturday, however, there was no sign of a breakthrough that would allow the audit to resume, adding one more day to Afghanistan’s lengthening political vacuum.