TRENTON, N.J. — Senator Frank Lautenberg of New Jersey, the oldest member of the Senate, announced Thursday that he will retire at the end of his current term rather than seek reelection at age 90 next year.

‘‘This is not the end of anything but rather the beginning of a two-year mission to pass new gun safety laws, protect children from toxic chemicals, and create more opportunities for working families in New Jersey,’’ Lautenberg said in a statement.