multilateralize
/ˌmʌltɪˈlat(ə)rəlʌɪz/ /ˌmʌltɪˈlat(ə)r(ə)lʌɪz/(also multilateralise)
verb
[with object] To make multilateral; to make party to a multilateral agreement; to regulate or administer on a multilateral basis.
Origin
1940s; earliest use found in Quarterly Journal of Economics. From multilateral + -ize.