Train managers on the line linking Britain to continental Europe will strike for seven days in August, part of a dispute over working too many unsocial hours, but only one or two trains will need cancelling, service operator Eurostar said.

Britain's RMT union, behind an ongoing strike on rail lines in southern England, said the Eurostar action would take place over two weekends, from 2301 GMT on Aug. 12 to 2259 GMT on Aug. 15, and from 2301 GMT on Aug. 27 to 2259 GMT on Aug. 29.

Eurostar said it would have to make small changes to its timetable to ensure all passengers booked to travel could do so. It may need to cancel one or two trains but passengers would be able to travel on later ones, the company said.

"Our focus has been seeking a joint resolution, naturally, while planning to provide a good service for our customers," a Eurostar spokeswoman said.

The RMT said 80 of its members objected to the balance of unsocial hours - early mornings, late evenings and weekends - which they were being asked to work. The union said 95 percent of them had backed strike action in a ballot.

"It is our view that the greater proportion of that (unsocial shifts) is allocated to our crew rather than the continent," RMT spokesman Geoff Martin said in an email.

Elsewhere, RMT members are in the middle of a five-day strike on rail services connecting London, Brighton and Gatwick Airport in a row over safety.

The RMT, one of Britain's most militant unions, says train operator Southern wants to extend the use of driver-only operated trains and so reduce the safety role that conductors play.

The Eurostar dispute centres on what the RMT called the company's failure to honour an agreement from 2008 which sought to ensure that train managers could expect a good work-life balance in terms of unsocial hours and duty rosters.

Eurostar, which is majority-owned by the French state rail operator SNCF, said efforts to resolve the dispute were ongoing and declined to comment on its details.

The RMT's Martin said talks had been suspended but he expected the strike announcement to "focus minds" and bring management back to the negotiating table.

He said the RMT expected the strike to have a major impact, noting that train managers had crucial security responsibilities and could not easily be replaced by agency workers. – Reuters