"We could be sacrificing our freedom to deploy the full range of missile defenses we need by agreeing to arms control agreements like START or other agreements or unilateral actions like the U.S. statement on missile defense accompanying the START treaty," Kyl said in a speech on May 19.
At a July 29 hearing, McCain said that "serious questions still remain about this treaty, specifically on the New START treaty's methods of verification, its potential constraints on our ballistic missile defense, and the accompanying plan for modernization of both the nuclear stockpile and our nuclear delivery vehicles."
McCain accused the U.S. negotiators of agreeing to language that would make it easier for Russia to cheat.
"This hearing is also an opportunity to try to learn why our negotiators agreed to a significantly weaker verification regime than that of the original START treaty it is to replace. So weak, in fact, that the potential for cheating is significant," he said.
The administration has reached out to Republicans to urge them to vote yes. Vice President Biden has reportedly held discussions with Senator Kyl, and in recent months Secretary of State Hillary Clinton has met with several senators to personally address their concerns. The Senate Foreign Relations Committee has held 12 hearings on the subject.
The administration hopes it can convince Senator Kyl to support the treaty, which would give other Republicans political cover to vote in favor as well.
Republicans have submitted over 700 questions to the administration about the pact. Some say this is evidence of GOP stall tactics, though Pifer says that may be more due to a lack of knowledge about the treaty than a stall tactic.
"The senate has not had to consider a serious arms control treaty now for twenty years. You don't have a level of expertise that you had say in the early 1990s when people were looking at START. People are relearning strategic arms control," he said.