* Ballot result on day BA and Iberia complete merger
* BA says strike would only affect short-haul flights
* BA says strike not backed by a majority of crew
(Adds BA comment, background, details)
LONDON, Jan 21 (Reuters) - British Airways cabin crew voted on Friday to strike again in a long-running battle over proposed job and pay cuts, casting a shadow over the completion of the airline's merger with Spain's Iberia.
The Unite union said that of 7,330 valid ballots, 78.5 percent backed strike action, while 21.5 percent opposed it.
No date was announced for any further strikes and the union left the door open to more talks.
"For the fourth time in 13 months, British Airways cabin crew have voted overwhelmingly in support of their union and expressed their dissatisfaction with management behaviour," Unite General Secretary-designate Len McCluskey said.
"This dispute will be resolved by negotiation, not litigation or confrontation, and it is to negotiation that BA management should now apply itself. We are ready," he added.
The dispute began last year over proposed cuts to pay and staffing levels. It has already cost the airline 150 million pounds ($240 million).
But the dispute has now broadened into a fight over issues related to last year's strikes.
The union is demanding that BA restore travel perks that it took away from cabin crew who took part in the original strikes. It also wants binding arbitration on disciplinary cases linked to the original dispute and the restoration of earnings docked from crew who were genuinely off sick on strike dates.
BA SAYS NO MAJORITY FOR STRIKE
BA said the ballot result showed Unite did not have the support of a majority of cabin crew for further strike action.
"Of our 13,500 crew, only 43 per cent voted in favour of strike action in this ballot," the company said in a statement.
It urged Unite to return to a deal being discussed last year which it said guaranteed pay rises for the next two years and secured terms and conditions for existing crew.
The airline accuses the union of going back on a promise to recommend that deal to its members.
The latest strike announcement was made on the day BA was due to complete its merger with Iberia. Shares in the new holding company, International Consolidated Airlines Group (IAG), will be listed in London and Madrid on Monday.
BA said before the ballot result it had drawn up contingency plans that would allow it to operate a "substantial proportion" of its short-haul flights, and all of its long-haul flights, at Heathrow airport in the event of another strike.
It said flights out of London's Gatwick and London City airports would be unaffected and would operate as normal.
BA was floated on the London Stock Exchange in 1987 at a price of 125 pence after it was sold to investors by the then Prime Minister Margaret Thatcher.
The two carriers will retain their brands as part of the deal, which will create Europe's second biggest airline by value behind Lufthansa, and is expected to save the pair 400 million euros ($540 million) a year by its fifth year.
IAG, which will have 419 aircraft flying to 205 destinations, wants to fold other carriers into the group and has drawn up a list of 12 airlines it is interested in buying. (Reporting by Keith Weir, Tim Castle and Rhys Jones; editing by Sophie Walker)