American aircraft company Boeing Co.'s largest union plans to hold a vote on a contract that would guarantee that the planned 777X jetliner would be assembled at unionized facilities in Washington state.

Wall Street Journal, quoting Boeing union's Frank Larkin, said the vote could take place as soon as January 3. It would decide on a Boeing offer made early this month for a new eight-year contract. Local union officials rejected the offer, but many members said they wanted the chance to vote on the proposal. Larkin is a spokesman for the international leadership of the International Association of Machinists and Aerospace Workers.

Union members last month overwhelmingly rejected a previous offer from Boeing. The said offer had sought deep concessions on wages and healthcare costs, as well as changes to retirement benefits. The union represents 32,000 Boeing employees, the report said.

Boeing has said approval of the contract is necessary for it to decide whether to make the 777X and its carbon-fiber composite wings in Washington. After its first offer was rejected, Boeing sought bids from other states to win the work for the 350-500-seat jetliner due in 2020, WSJ said.