Boeing and its largest union said they would continue contract talks on Tuesday, as both sides seek an agreement to end a strike by around 33,000 U.S. West Coast factory workers.

The company and the union, whose members have been on strike for 25 days, had resumed contract talks on Monday in the presence of federal mediators.

"Although we met with Boeing and federal mediators all day, there was no meaningful movement to report. We will be back at it tomorrow," The International Association of Machinists and Aerospace Workers said late on Monday.

Boeing also confirmed mediation would continue on Tuesday.

The union is seeking a 40% pay rise over four years and the restoration of a defined-benefit pension that was taken away in the contract a decade ago.

Boeing made an improved offer last month that it described as its "best and final", which would give workers a 30% raise and restore a performance bonus, but the union said a survey of its members found that was not enough.

The strike has halted production of Boeing's best-selling 737 MAX jet, along with its 777 and 767 widebody planes. The MAX is a key revenue-driver for the company at a time when it is struggling with weak margins in its defense business.