In the mid-1990s with the return of US-Russian cooperation in space, NASA agreed to provide funds to complete the Spektr and Priroda modules in exchange for having 600 to 700 kg of US experiments installed.
Anos máis tarde os Estados Unidos acordaron con Rusia proporcionar fondos para rematar os módulos Spektr e Priroda a cambio de levar a bordo entre 600 e 700 kg de experimentos americanos.