Irish unions ask members to back all-out picket

* Unions to urge members to join all-out picket

* Talks to be held on Wednesday to resolve dispute

DUBLIN, July 7 (Reuters) - The union representing striking Irish electricians said on Tuesday that other affiliates of the Irish Congress of Trade Unions had agreed to hold ballots and ask their members to support them with an all-out picket.

Employers hope talks with unions on Wednesday will help end the strike they fear could cripple industries already weakened by one of the deepest recessions across the developed world.

But the union representing the 10,500 contractors taking part in the indefinite strike over wages -- the first major industrial action since Ireland went into recession last year -- remained defiant.

"Our pickets have already made an enormous impact on the electrical contracting and construction sectors and this will be multiplied many times over once the all-out pickets are put in place," the Technical Engineering and Electrical Union (TEEU) said.

The dispute centres around wage increases of about 11 percent the electricians say they are owed for a number of years.

Employers have said they cannot afford to give them more money and instead are looking for a wage cut of 10 percent.