PARIS (Reuters) - French train services were severely disrupted on Tuesday as tens of thousands of state railworkers protested over plans to reduce rest periods and other protective work practices in preparation for Europe-wide deregulation.

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The third strike in two months halved high-speed train services and cut other intercity rail journeys to as few as one in three, although international Eurostar and Thalys connections appeared largely unaffected by the 24-hour stoppage.

At issue is a fundamental rewrite of working conditions that management at the SNCF state railway company hopes will enable it to cope when EU-wide legislation throws national passenger services open to competition in 2020.

“For the moment this is just a massive warning strike,” said Philippe Martinez, head of the large, hardline CGT union.

With the exception of Britain, which entirely privatized its railways in the 1990s, most EU countries have limited deregulation to the pace set by common accord at European Union level, starting with freight in 2006 and a few cross-border links thereafter.

In France, where the TGV high-speed network is the world’s second-biggest after Japan, the stakes are particularly high. A staff of around 150,000 is often singled out as enjoying enviable job and pension rights under decades of monopoly status.

Despite predictable resistance from more militant unions such as the CGT and Sud-rail, however, the latest stoppage is also being backed by unions like the more conciliatory CFDT on the grounds that low-cost competition should not set the standard.

“The CFDT will never put its name to a regression in work and transport safety standards,” the CFDT union said in a statement explaining why it was joining Tuesday’s strike call.

The CFDT and other unions are angry over a proposal seeking to scale back myriad guarantees that would, for example, align the number of work-free weekends per year with the lower level private operators accord their staff.

The proposal -- a first draft on which an agreement is being sought by July -- is part of a broader package that is set to establish a standard across the rail passenger sector when it is opened up to full-on competition, firstly on high-speed lines in 2020 and more broadly in 2026.

Beyond the chaos caused for commuters heading into large urban centers such as Paris, local media highlighted that the impact of the train strike was mitigated by people traveling by coach.

This form of transport has mushroomed in France as a low-cost alternative since the Socialist government liberalized that business last year.