Some Republicans remain opposed to language in the treaty's preamble, which Russian officials have said they believe limits future development of US missile defense programs. Congressional Democrats and the White House say the preamble language is not legally binding. The Senate on Saturday defeated an amendment offered by Sen. John McCain to strike the controversial -- and allegedly non-binding -- language from the preamble.
The White House says it expects the treaty to be ratified before the current Congress adjourns. Democrats need the support of ten Republicans to reach the Constitutionally-required 2/3 threshold for passage of international treaties. That task became one vote more difficult when Oregon Senator Ron Wyden left the session to pursue cancer treatments.