The Unite trade union will open a strike ballot for British Airways cabin crew on January 25 after two weeks of talks with the airline failed to secure a deal on changes to working conditions, it said on Monday.

The vote is expected to take about a month and, if the almost 13,000 crew affiliated to Unite agree to strike, a walkout could begin from the beginning of March.

The union said last month it would move to a new ballot after a planned Christmas strike was ruled unlawful.

"We have told (BA) management all along that this dispute, and the damage it does to BA's prospects, can only finally be resolved through negotiation," Len McCluskey, assistant general secretary of Unite, said in a statement.

"That remains our position, and I hope the company will make the best use of the time available before the ballot closes."