May 29 (Reuters) - Boeing and a union representing about 125 of its firefighters said Wednesday they had reached a tentative contract deal, the planemaker and union said in a joint statement.

Boeing in early May locked out members of the International Association of Fire Fighters (IAFF) Local I-66 after they rejected two contract offers - a move that drew the concern of President Joe Biden.

Boeing and IAFF Local I-66 said they expected results of a vote Thursday on the deal "that would end the lockout and months of negotiations. This tentative agreement addresses the needs of our firefighters and the company."

If the deal is approved, firefighters are expected to return to work Saturday.

At a May 14 rally outside Boeing headquarters in Arlington, Virginia, IAFF President Edward Kelly, AFL-CIO President Liz Shuler and Representative Val Hoyle urged Boeing to make a deal. Last week, House lawmakers from Washington State urged both sides "to negotiate in good faith toward an agreement."

Boeing and the union did not immediately disclose details of the agreement. Boeing said in early May it had offered to increase firefighters' average take-home pay from $91,000 to $112,000 in the first year.

The International Association of Machinists and Aerospace Workers (IAM) is separately negotiating a new contract on behalf of over 30,000 workers who build Boeing's 737 MAX jets.

Boeing 737 MAX production has fallen sharply as the Federal Aviation Administration (FAA) steps up factory checks following a panel blowout on a new Alaska Airlines 737 MAX 9 in January, blamed on an assembly error. Boeing is set to meet with the FAA on Thursday on its 90-day plan to boost quality. (Reporting by David Shepardson Editing by Mark Potter)