Boeing workers are set to go on strike after they rejected a tentative deal between union representatives and the plane maker that included a 25% pay rise.

More than 30,000 workers - who produce planes including the 737 Max and 777 in the Seattle and Portland areas - could join the walkout which is set to start in a few hours.

It is yet another setback for the aviation giant, which is facing deepening financial losses as it struggles to repair its reputation after a series of safety issues, including two fatal crashes.

It is also a major blow for Boeing's new chief executive Kelly Ortberg, who was appointed last month with a mission to turn the business around.

Earlier this week, union representatives advised members to support the tentative deal.

Mr Ortberg also made a last-ditch plea to workers, warning that a strike would put the company's "recovery in jeopardy".

As well as a 25% pay rise over four years, the preliminary agreement included a commitment from Boeing to build its next commercial plane in the Seattle area if the project started during the lifetime of the contract.

The union initially targeted a number of improvements to workers' packages, including a 40% pay rise.

The current contract between Boeing and the unions was reached in 2008 after an eight-week strike.

In 2014, the two sides agreed to extend the deal, which is due to expire at midnight on Thursday.