PARIS - Trade unions told France's new Prime Minister Jean Castex that he should focus on rescuing the French economy from deep recession and saving jobs rather than re-opening negotiations on overhauling the byzantine pension system.

The pandemic halted the reform, the single greatest revamp of the pension system since World War Two, in its tracks in February, and presents President Emmanuel Macron with a tough political decision as he seeks to recast his presidency.

Deferring the reform, which includes raising the retirement age by two years to 64 to collect a full pension, until after the 2022 presidential elections might win union and voter support. But it would undermine his already-weakened credibility as a reformer. 

On the eve this week's government reshuffle, Macron said he was not going to jettison the reform. Castex on Wednesday said the focus now should be on the financing of the pension system, one of the most generous among industrialised nations.

"Clearly, the priority today is jobs," said Laurent Berger, head of the reform-minded CFDT union, which backs the reform's aim of unifying the myriad pension funds into a single, point-based system.

Berger spoke after meeting the prime minister, who is hosting all unions individually ahead of a resumption of talks the premier wants before July 20.

The pension reform is central to Macron's ambition of creating a more flexible and competitive labour force. But it has infuriated trade unions who argue the reform will erode hard-earned benefits and leave pensioners worse off.

The reform triggered a wave of street protests and public transport strikes that lasted weeks at the turn of the year.

Underscoring the financing crunch, the independent pensions advisory body COR forecast the pension deficit would balloon to 29.4 billion euros in 2020 from a previously anticipated 4.2 billion euro shortfall, due to a sharp decline in contributions.

"There are other ways to find the 25 billion (than raising the retirement age)," said Yves Veyrier, leader of the hardleft Force Ouvriere union.

(Reporting by Caroline Pailliez; Writing by Richard Lough; Editing by Chizu Nomiyama) ((Email: richard.lough@thomsonreuters.com; Tel: +33 1 49 49 52 42;))