The uncertainty of refueling dollars for the USS George Washington, strained funding for amphibious warships, and challenges to the Ohio Replacement Program all present serious complications for the Navy's goal of reaching a 300-ship fleet in coming years.

Several analysts and watchdog groups say the dollars simply are not there to support the Navy's fleet size goals.

The prospect of sequestration returning in 2016 and the $15 billion overall budget reduction within its 2015 budget proposal place additional pressure on the Navy's shipbuilding ambitions.

Yet Navy Secretary Ray Mabus and other service leaders have recently said the service is on pace to achieve a fleet size of 300 ships by the end of the decade.

"In the past four years, we have arrested the decline in the size the fleet. Since May 2009, we have put 60 ships under contract and are on pace to return the fleet to 300 ships before the end of the decade," Mabus told lawmakers at a recent budget hearing.

Navy officials say a new 30-year shipbuilding plan will be finalized over the next several weeks.

"The force structure assessment of 2012 does call for 306 ships," said Lt. Caroline Hutcheson, a Navy spokeswoman. "We believe this number accurately and appropriately captures the requirement for Navy combatant ship capacity and capabilities. The Navy will continue to evaluate the future demand for forces, maintaining a balance between force structure requirements while managing fiscal and operational risk."

However, members of Congress and defense analysts question how the Navy expects to attain a 300-ship fleet.

"I continue to believe that, at current funding levels, the Navy will not meet its minimum fleet requirement of 306 ships in the coming years. The administration has continually under-resourced the shipbuilding budget, making the 30-year shipbuilding plan little more than a fantasy document," said Rep. Randy Forbes, R-Va., chairman of the House Armed Services Committee Seapower and Projection Forces Subcommittee.

One analyst said numbers and assessments from the Congressional Budget Office analysis suggest that what the Navy actually spends on shipbuilding is much lower than the amounts it plans or wants to spend.

"The Navy is historically over-optimistic about what it will be able to do and optimistic about how much money it is going to get for shipbuilding. I think we will have a smaller fleet than the Navy says," said Benjamin Friedman, a defense fellow at the Cato Institute, a Washington D.C.-based think tank.

The CBO's analysis of the Navy's 2014 Shipbuilding Plan states the costs of carrying out the 2014 plan at $21 billion per year are one-third higher than the funding amounts that the Navy has received in recent decades.

In short, the cost of the Navy's projected shipbuilding plan greatly exceeds the amount of actual money being spent on shipbuilding, which is about $16.8 billion per year, the CBO explains.

Given the rate at which ships are retiring from the fleet, the CBO claims its ship construction plans from 2014 to 2043 will not achieve a fleet of 306 ships until 2037.

Virtually all of the Navy's major acquisition and construction programs are experiencing budgetary pressure and impacts, leading many to wonder if the service will have the dollars needed to execute its vision.

Many lawmakers have raised concerns about funding for the Navy's ballistic missile submarine program, the Ohio Replacement Program, or ORP. The Navy hopes the submarines, now in the technology development phase, will wind up costing less than $5 billion once production commences.

However, if the money for the Ohio Replacement Program materializes as expected, some lawmakers have wondered if funds will be drained from other needed ship building accounts such as amphibs, carriers and cruisers.

Rep. Mike McIntyre, D-N.C., suggested that Congress set up a special account dedicated to the funding of the Ohio Replacement Program to ensure the high-priority program gets funded in a manner that can safeguard other accounts.

"There is the potential of setting up an account perhaps similar to the national defense sealift fund which Congress established in the 1990s," he said at a recent budget hearing. "With such an account, the Navy would be able to spread the burden of replacing this ability without gutting the rest of our ship building budget."

The first Ohio Replacement Submarine is slated to begin production in 2021. It will enter service by 2031. The Ohio Replacement-class submarines are expected to serve through 2085 and conduct as many as 124 patrols per year, service officials said. The technology development is now being worked on by Electric Boat, a division of General Dynamics, under a five-year, $1.85 billion deal.

When it comes to amphibs, service leaders say they will come up short of the 33 amphibious warships which the Navy and Marine Corps deemed an acceptable number. However, the overall number of amphibs required by both services is actually at 38 ships, service leaders said. Thirty-three was only a number arrived upon as the absolute minimum, provided at least 30 amphibious warships are available at any given time.

Budgetary strain has led to the cancellation of the 12th LPD amphibious transport dock, leaving the number of amphibious transport docks at 11.

"Operationally, we sure could use the [12th] LPD," Gen. John Paxton, assistant commandant of the Marine Corps, told lawmakers at an April 2 budget hearing before the Senate Subcommittee on Seapower.

Paxton said the cost of new amphibs, at more than $2 billion each, is prohibitive. He also added that maintenance and sustainment costs for amphibs compound the challenges of getting to a 33-ship fleet.

"For the next five years, the amphib fleet is not going to be at 33," Paxton told lawmakers.

Meanwhile, the question of whether the Navy will maintain its congressionally mandated requirement to operate 11 aircraft carriers remains entirely unresolved. Although current law requires the Navy maintain 11 carriers, the question of whether the service will drop to 10 hangs amid an air of uncertainty.

The issue hinges upon whether there will be money made available to refuel the USS George Washington at its mid-life point so that it can serve the remaining 25 years of its intended lifespan.

The Navy wanted to spend the $5.7 billion to refuel the carrier, but that money was not part of the 2015 budget submission. Now the issue of available funds for the USS George Washington depends upon whether sequestration budget levels return in 2016, per the budget control act, service leaders said.