UPDATE 1-Boeing makes contract offer to engineers union

* Boeing agrees to extend some terms of expired contract for four years

* Health care plans to remain with no rise in employee contribution

* Pension basic benefit to rise

Jan 17 (Reuters) - Boeing Co agreed to extend the terms of its previous contract for 23,000 employees represented by an engineers union, except for new proposals that both parties agreed to during talks.

Boeing said its "best and final" proposal to the Society of Professional Engineering Employees in Aerospace (SPEEA) would roll forward the contract for four years.

"Agreeing to this contract as soon as possible will allow all of us to focus our time and energy on the immediate challenges facing the company," Boeing said in a statement.

Under the offer, existing employees "would see salary pools of 5 percent annually for the duration of the contract", Boeing said.

The company's health care plans would remain in place with no increase in employee contributions, and the pension basic benefit would be increased, Boeing added.

SPEEA made its own "best and final" contract offer to Boeing on Wednesday, proposing to extend the contract for four more years and averting a strike to allow the aerospace company to focus on addressing safety concerns customers have with the new 787 Dreamliner.

A SPEEA spokesman was not immediately available for a comment outside of regular business hours.

The negotiations with SPEEA have been going on since April 2012. The previous contract expired in October.