Reuters reported on Monday that Philippine President Rodrigo Duterte was ready to make a deal with the Islamic State to end the siege of Marawi in its early days but changed his mind without explaining why.

The battle for Marawi has now lasted over six weeks and has all but devastated the city, between the actions of ISIS-aligned militants and airstrikes by the Philippine military.

The Reuters report is based on the testimony of Muslim leader Agakhan Sharief, who said he was asked by a senior Duterte aid to act as an intermediary with the Maute terrorist group. The Maute are violent Islamist separatists who attacked Marawi after the Philippine military attempted to capture the leader of an allied gang, Isnilon Hapilon of Abu Sayyaf.

The Maute group is led by a pair of brothers, who were supposedly planning to send their mother by helicopter to meet with Duterte for talks. Sharief said the government agreed to provide the requested helicopter transportation. He said allowing the separatists to implement Islamic sharia law in the Maute hometown of Butig was one of the chips Duterte was prepared to put on the table, and the rebels were interested in taking the deal.

Reuters reports that two other “sources familiar with the matter” confirmed that Duterte was working behind the scenes to arrange negotiations with the Maute but abruptly ended the process by giving a speech about a week after the siege began, in which he declared his government would “not talk to terrorists.”

Mother Maute ended up getting arrested in early June, as did the father of the terrorist leaders. Yet another member of the large insurgent family was detained by Philippine authorities on Wednesday: the niece of the Maute matriarch, described as “the main financier and logistic supporter of the militant group.”

The mayor of Marawi also said negotiations with the insurgents were undertaken, but he blamed their speedy collapse on the terrorists’ refusal to ease up their attacks on government forces.

However, some other named sources were willing to go on the record and deny back-channel negotiations were ever launched, including Duterte’s national security adviser, Hermogenes Esperon.

Sharief chalked up the termination of the potential peace talks to Duterte’s mercurial nature. “The problem with our president, his mind is changing always,” he said.

On the other hand, it seems rather unlikely that senior Islamic State management would have been willing to settle for imposing sharia law on one town as the payoff for ending hostilities in the southern Philippines.

The battle of Marawi has killed 337 militants, 85 Philippine troops, and 44 civilians to date by Reuters’ tally, along with forcing 260,000 people to flee their homes. Philippine government forces are struggling to keep the battle contained to one city.