UPDATE 3-Irish strike halts construction projects, brewing

* 10,500 striking electricians to call for all-out picket

* Major union says it would be in favour of joining them

* Production hit at Diageo's Guinness brewery in Dublin

* Pickets at power plants, output unaffected

(Adds fresh comments on impact)

By Ashley Beston

DUBLIN, July 6 (Reuters) - A union representing thousands of striking electricians in Ireland said on Monday it would call for an all-out picket of over 200 construction sites, escalating a dispute that also hit the output of Ireland's favourite beer.

"Our members have sent a very clear signal to the employers by their actions this morning that they will not be rolling over and meekly accepting cutbacks to bail out developers and speculators," said Eamon Devoy, general secretary-designate of the Technical Engineering and Electrical Union (TEEU).

"We will now be seeking to consolidate the support we are already receiving from other workers through an application for an all-out picket," he said in a statement.

About 10,500 contractors are taking part in the indefinite strike, the first major industrial action since Ireland went into recession last year. Pickets have been set up at building sites at Dublin Airport and at companies such as Intel (INTC.O), Pfizer (PFE.N) and Microsoft (MSFT.O).

A court granted an injunction against TEEU to stop picketing the St. James's Gate brewery owned by Diageo (DGE.L), one of the world's biggest alcoholic drinks groups, where a strike by third-party contractors severely affected Guinness production.

Because of the delicate yeast-based brewing process, even a relatively short stoppage could potentially affect output of Ireland's favourite stout for weeks, the company said.

SIPTU, one of Ireland's biggest unions with 200,000 members, has said it would support an all-out strike and if umbrella group ICTU, which represents most unions in Ireland, agrees to the electricians' request that could close most of the affected construction projects.

ICTU will need to ballot its members before making a final decision, which could take at least until next week.

Employers' group IBEC said the strike could force manufacturers to lay off workers, with some already put on protective notice in anticipation of further disruption.

The dispute centres around wage increases of about 11 percent the electricians say they are owed for a number of years. A contractor currently earns 21.49 euros ($30) per hour.