The Navy's proposed FY2015 budget requests $1,219.3 million for continued research and development work on the Ohio replacement program (ORP), a program to design and build a new class of 12 ballistic missile submarines (SSBNs) to replace the Navy's current force of 14 Ohio-class SSBNs. The Ohio replacement program is also known as the SSBN(X) program. The Navy has identified the Ohio replacement program as its top priority program. Under the Navy's FY2012 budget, the first Ohio replacement boat was scheduled to be procured in FY2019, and Ohio replacement boats were to enter service on a schedule that would maintain the Navy's SSBN force at 12 boats. The Navy's FY2013 budget deferred the procurement of the first Ohio replacement boat by two years, to FY2021. As a result of the deferment of the procurement of the lead boat from FY2019 to FY2021, the Navy's SSBN force will drop to 11 or 10 boats for the period FY2029-FY2041. The Navy says the decline to 11 or 10 boats during this period will be acceptable in terms of meeting strategic nuclear deterrent mission requirements because none of the 11 or 10 boats during that period will be encumbered by lengthy maintenance actions. The Navy in June 2014 estimated the procurement cost of the lead ship in the program at $12.4 billion in constant 2014 dollars, including $4.8 billion in detailed design and nonrecurring engineering (DD/NRE) costs for the entire class, and $7.6 billion in construction costs for the ship itself. The Navy in April 2014 estimated the average procurement cost of boats 2 through 12 in the Ohio replacement program at about $5.36 billion each in FY2010 dollars, and is working to reduce that figure to a target of $4.9 billion each in FY2010 dollars. Even with this cost-reduction effort, observers are concerned about the impact the Ohio replacement program will have on the Navy's ability to procure other types of ships at desired rates in the 2020s and early 2030s.