Signaling an abrupt thaw between Creative Artists Agency and Artists Management Group, Natalie Portman has become the first major client to sign with the agency while being managed by the company that’s in the process of being acquired by the Firm.

Portman, who was signed by CAA partner Bryan Lourd, is managed by Aleen Keshishian, who had been at AMG and is expected to join Rick Yorn and Julie Silverman-Yorn in the merging of AMG and Firm manpower.

Portman opens May 16 in the starring role of “Star Wars: Episode II — Attack of the Clones.” She is negotiating to play a supporting role opposite Jude Law, Nicole Kidman and Renee Zellweger in the Anthony Minghella-directed Miramax/MGM co-production “Cold Mountain.” Portman starred in the Mike Nichols-directed staging of “The Seagull” in Central Park last summer and begins filming the third leg of the “Star Wars” prequel next summer.

Now that Michael Ovitz is bowing out of AMG’s management business, it was not unexpected that relations between managers and CAA would improve. The cold war has lasted several years, going back to when CAA declared agency co-founder Ovitz a competitor when Robin Williams left CAA to join his management concern. At that time, CAA unilaterally refused to rep AMG clients and lost several prominent ones who were forced to choose. Several have left AMG and returned to the CAA fold, Williams included. Portman, who had been repped by ICM, becomes the first to have ties to both CAA and the management company.

— Michael Fleming