The Russian Duma is expected to approve an agreement with Ukraine that will regulate cooperation between the two countries on maintaining the R-36M2 missiles (SS-18, also known as 15A18M). The missiles, listed in the agreement by the name of the entire system they are part of, 15P118M, were originally designed and produced in Ukraine.
The agreement was signed two years ago - in March 2006, but hasn't been ratified until now. It was reported that the cooperation with Ukraine will allow Russia to extend service life of R-36M2 missiles by additional ten years to 25 year. The missiles, deployed in the late 1980-early 1990s, are expected to reach the retirement age by 2014-2016.
UPDATE 02/12/08: President Putin signed the agreement into law on February 12, 2008.