The New START treaty maintains US nuclear and missile defence.

The US’ Nuclear armament will be modernized along with New START. “The Obama administration has agreed to provide for modernization of the infrastructure essential to maintaining our nuclear arsenal. Funding these efforts has become part of the negotiations in the ratification process. The administration has put forth a 10-year plan to spend $84 billion on the Energy Department's nuclear weapons complex. Much of the credit for getting the administration to add $14 billion to the originally proposed $70 billion for modernization goes to Sen. Jon Kyl, the Arizona Republican who has been vigilant in this effort. Implementing this modernization program in a timely fashion would be important in ensuring that our nuclear arsenal is maintained appropriately over the next decade and beyond.”[1] Both US Military and civilian leaders insist that the new START treaty will still allow the US to deploy effective missile defenses, something which Russia was opposed to, and so will not affect US missile defense plans. The main limit on missile defense is that the treaty prevents the conversion of existing launchers for this purpose this would be more expensive than building new missiles specifically for defense purposes. [2]   Furthermore, as Joe Biden argues, New START is important to Russian cooperation on missile defense: "This [missile defense] system demonstrates America's enduring commitment to Article 5 of the Washington Treaty—that an attack on one is an attack on all. NATO missile defense also provides the opportunity for further improvements in both NATO-Russian and U.S.-Russian relations. NATO and Russia agreed at Lisbon to carry out a joint ballistic missile threat assessment, to resume theater missile-defense exercises, and to explore further cooperation on territorial missile defense—things that were nearly unimaginable two years ago. These agreements underscore the strategic importance the alliance attaches to improving its relationship with Russia. But trust and confidence in our relationship with Russia would be undermined without Senate approval of the New Start Treaty, which reduces strategic nuclear forces to levels not seen since the 1950s, and restores important verification mechanisms that ceased when the first Start Treaty expired last December."[3] In many ways, in the 21st Century having an abundance of nuclear weapons, particularly having too many, is more of a liability than an advantage. The United States will be far safer with fewer nuclear weapons in the world and a stronger, more stable relationship with Russia under New START, and this is desirable. Therefore it is clear that New START maintains the important parts of US nuclear capabilities while removing the over-abundance which may become a liability due to security and medical concerns, and so New START should be supported. [1]Kissinger, Henry A. ; Shultz,  George P. ; Baker III, James A’ ;  Eagleburger , Lawrence S. ; and Powell, Colin L. "The Republican case for ratifying New START". Washington Post. 2 December 2010. http://www.washingtonpost.com/wp-dyn/content/article/2010/12/01/AR2010120104598.html?hpid=opinionsbox1 [2] ibid [3] Biden, Joseph. "The case for ratifying New START". Wall Street Journal. 25 November 2010.  http://online.wsj.com/article/SB10001424052748704074804575631051668226566.html?mod=googlenews_wsj