PARIS, Sept 27 (Reuters) - French President Emmanuel Macron said on Sunday he would not give up on an initiative to save Lebanon from collapse, but that he was "ashamed" of Lebanon's leaders and would increase pressure on them to change course.

Lebanon's prime minister-designate, Mustapha Adib, quit on Saturday after failing to line up a non-partisan cabinet, dealing a blow to the French plan aimed at rallying sectarian leaders to tackle the country's crisis.

"I am ashamed of Lebanon's political leaders," Macron told a news conference in Paris. "The leaders did not want, clearly and resolutely, to respect the commitments made to France and the international community. They decided to betray this commitment."

Adib was picked on Aug. 31 to form a cabinet after Macron's intervention secured a consensus on naming him in a country where power is shared out between Muslims and Christians.

Under the French roadmap, the new government would take steps to tackle corruption and implement reforms needed to trigger billions of dollars of international aid to fix an economy crushed by a huge debt.

But there was deadlock over a demand by Lebanon's two main Shi'ite groups, Amal and the heavily armed Iran-backed Hezbollah, that they name several ministers, including finance, who will have a big role in drawing up economic rescue plans.

Macron criticised both parties for blocking efforts to form a government by a mid-September deadline.

"I understood that the goal of Hezbollah was to make no concessions ... The failure is theirs," he said.

Macron said political leaders had chosen "to deliver Lebanon to the game of foreign powers", destabilising the region.

He gave Lebanon's political class four to six weeks to implement his roadmap, and said he would commit to holding a donor conference for Lebanon in October. He ruled out immediate sanctions. (Reporting by John Irish and Matthias Blamont; writing by Raya Jalabi, editig by Timothy Heritage)