The 45-year-old centrist leader is facing a major domestic crisis over his flagship pensions reform, whose headline measure is to raise the legal retirement age to 64 from 62.

Some demonstrations have turned violent since Macron's government forced the bill through parliament last month without a vote, using an executive power that is legal but has sparked accusations of undemocratic behaviour from opponents.

'Macron imposes, we explode,' read one protester's sign in Paris on Thursday / © AFP

The Constitutional Council's green light is the final hurdle before Macron can sign the changes into law and ensure they are implemented by year-end.

But labour unions and opposition lawmakers hope for a rejection of a reform that Macron put at the heart of his re-election campaign last year for a second term in office.

Some 380,000 people took to the streets nationwide on Thursday in the latest day of union-led action against the bill since January, according to the interior ministry.

But that was far fewer that the nearly 1.3 million it said demonstrated at the height of the protests in March.

Momentum has petered out in recent weeks as people appear to become increasingly weary of sacrificing a day's pay to strike or march.

- Partial approval? -

Paris police have banned any demonstration around the Constitutional Council in Paris until Saturday morning.

The court is to issue two decisions by the end of the day.

Police have banned any demonstration around the Constitutional Council until Saturday morning / © AFP

First, the nine-member council is to rule on whether the pensions overhaul, which has been formulated as a social security budget law, is in line with the constitution.

Experts think the most likely scenario is that it will partially approve the bill.

That means it may scrap some details of the law as inappropriate for that kind of legislation, but it will probably throw its weight behind its core elements, including pushing back the minimum legal age for retirement.

Second, the court is to look into two separate requests from the left-wing opposition to launch a possible referendum on an alternative law to limit the retirement age to 62.

It is not yet clear whether it will give its go-ahead, but the path towards any actual referendum would be very long.

For any vote, the opposition would need to collect some 4.8 million signatures from members of the electorate backing their proposal within nine months.

And a referendum would take place only if both chambers of parliament refused to examine the bill in the next six months -- something regarded as unlikely.

- 'End to procedures' -

Having repeatedly dismissed calls for talks with union leaders in recent weeks, Macron has said he will invite labour representatives for discussions once the court decision is published.

EU retirement ages on the rise / © AFP

"The decision from the Constitutional Council on Friday will bring an end to the democratic and constitutional procedures," Macron told reporters on a trip to the Netherlands on Wednesday.

He added however that public debate "will continue, for sure".

CFDT union leader Laurent Berger has said that if the bill is only partially approved, it should be re-examined in parliament.

Surveys show that about two in three French people are against the pension changes, with critics arguing they are unfair for women and unskilled workers who started working early in life.

But the government argues that they are essential to stop the system from falling into heavy deficits in coming decades, and bring France in line with the rest of Europe where people typically retire later.

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