Image copyright fgw Image caption First Great Western's new high-speed trains will replace a fleet dating back to the 1970s

A strike by rail workers at First Great Western is set to go ahead this weekend after the latest talks aimed at finding an agreement failed.

Members of the Rail, Maritime and Transport union are due to walk out for three days from Saturday.

The union is in dispute over the introduction of new high-speed trains, a move which it says will hit jobs and on-board catering.

Services from London to south Wales and south-west England face disruption.

The union's general secretary Mick Cash told members that urgent talks had been held with the company, but no agreement had been reached.

A spokesman for First Great Western said "positive" talks were held with the union on Tuesday.

"We have once again reiterated that our proposals do not involve running the new trains without a qualified train manager on board and that our plans mean recruiting at least 100 more on-board staff, not less," he said.

Further discussions were planned for later this week, he added.

Union members held a 48-hour strike over the same dispute in July and a 24-hour one on Sunday.

The first Hitachi trains will run on the Great Western main line from 2017 and the East Coast main line from 2018.