France "regrets" that Lebanon has been unable to form a new government after a mass resignation in the wake of a deadly explosion in Beirut's port last month, President Emmanuel Macron's office said on Wednesday.

"It's not too late," the French statement said, after the expiry of a mid-September dateline set by Macron, who has set himself up as a broker for finding common ground among Lebanon's rival political factions.

The statement called on officials to help the premier-in-waiting Mustapha Adib "form a government that is up to dealing with the gravity of the situation".

Macron is pushing for a revamped cabinet that will address urgently needed overhauls to get Lebanon's economy back on its feet, and address the deep public anger over the August 4 port blast that killed 191 people.

For many Lebanese, the disaster resulted from longstanding corruption and ineptitude among a political class that has failed to establish a functioning state or uphold the rule of law.

The French president has visited Beirut twice since the disaster to try to forge a working consensus for a reform-minded government, warning that he will block recovery funds from donors if no progress is made.

"We are continuing to closely follow the situation and pursue our contacts with Lebanese political leaders to renew our insistence in this matter," Macron's office said.