French President Emmanuel Macron promised on Friday that the restoration of Paris's Notre Dame Cathedral, badly damaged by fire in 2019, would be completed in time for its planned reopening next December.

"We will meet the deadline," Macron told reporters while he inspected the site, exactly one year ahead of the scheduled date.

Macron had initially promised to have Notre Dame restored within five years, in time for the Paris Olympics next summer.

But after early setbacks in the rebuilding effort, he set a new deadline.

Restoration of the UNESCO-listed building, which had 12 million visitors a year, has hit several snags since people around the world watched aghast as its steeple crashed down in the blaze on April 15, 2019.

Its new spire has now started to emerge against the French capital's skyline and is expected to be fully completed when the city hosts the Olympics.

Behind the scaffolding, hundreds of workers are racing against the clock to restore the rest of the cathedral in time for it to reopen to the public on December 8, 2024.

The monument's new spire is identical to the previous one, designed by 19th-century architect Eugene Viollet-Le-Duc.

Its oak structure is to reach its full height of 96 metres (315 feet) by the end of the year.

It will then be covered in lead ornaments before the scaffolding is taken down.

- ' Perpetual reconstruction' -

The frames of the nave and the choir of the cathedral, which were also destroyed, are then due to be completed, after which the reconstruction of the roof can begin.

The initial five-year time frame was scrapped when rebuilding was delayed for months by decontamination efforts, after more than 300 tonnes of lead from the roof melted in the fire.

Authorities then had to halt work several times over the first winter due to high winds, before France went into lockdown in early 2020 to fight the spread of coronavirus.

More than five years after the blaze, three investigating judges are still looking into what sparked it.

An initial enquiry pointed to it probably being an accident, with an electrical fault or a cigarette among the theories.

Macron said there would be a competition for the design of six contemporary stained-glass windows for the cathedral -- the only "21st-century touch" to the monument, which will otherwise be rebuilt exactly as it was.

Macron also announced the creation of a museum in central Paris dedicated to Notre Dame, its history, its art "and its perpetual reconstruction".