In 2016, then-presidential candidate Donald Trump made the idea of building up a 350-ship Navy a cornerstone of his stump speech, complaining that the U.S. military was failing to meet the threat of potential adversaries and was increasingly vulnerable in the face of new generations of ship-killing missiles and stealthy submarines.

Unsurprisingly, just a month after Trump's election, the Navy released a brand-new plan calling for a 355-ship fleet - a massive leap from the 308 ships it was planning on building by 2021. The new number is now the "minimum force structure" required to keep up with demand, the Navy said in its new assessment.

But a year after releasing that assessment, the Pentagon still has not released an outline or a budget for how it plans to add those 47 new ships, or what those ships might do. More ships requires more money, and with current budget caps that don't expire until 2022 and a scheduled modernization of the submarine fleet already on the books, it will be difficult to undertake any sort of buildup.

"I think it's going to be very hard for them to work this into the budget in any sort of realistic way," said Todd Harrison, a budget analyst at the Center for Strategic and International Studies.

Internal Pentagon doubts about the larger Navy spilled into the public eye last month, when acting Navy Undersecretary Thomas Dee told a conference in Washington that a 355-ship Navy would take at least another 30 years to build.

His boss, Navy Secretary Richard Spencer, appeared on MSNBC days later to chide Dee, calling him "an acting placeholder" who didn't speak for the administration. "I need to get my team there who are aligned with our vision," he said. (On Nov. 13, the Senate Armed Services Committee approved the nomination of Thomas Modly for Navy undersecretary, sending his name to the full Senate for final confirmation.)

Spencer wouldn't commit to a timeline for getting to 355, saying that a decade is "pretty aggressive." The Congressional Budget Office has suggested it would take 18 years to reach 355, while the House Armed Services Committee thinks it could take 25 to 30 years.

The push for more chips comes as policymakers in Washington worry over rapidly advancing Chinese and Russian military capabilities. The U.S. Navy has also blamed the twin collisions of the USS Fitzgerald and USS John S. McCain in the Western Pacific this past summer on tired crews who hadn't received the necessary training due to constant deployments.

"There's so much riding on the upcoming National Defense Strategy," said one congressional staffer, referring to a review that is expect to spell out how and where the military will operate. The service is waiting on the document, which Pentagon analysts are readying for release early next year, before announcing its plans, he said.

A spokesperson for the Navy also told Foreign Policy that there are no immediate plans to release a 30-year shipbuilding plan, which was last updated in May 2016. The Navy normally releases the plan with each annual budget request, but it skipped 2017 with little explanation. The 2016 document laid out the strategy for increasing the fleet to 308 ships.

Navy Secretary Spencer "wants to be innovative, he wants to restart the magic of the Reagan buildup," which pumped billions into the Pentagon, the congressional aide said.

The secretary has been looking at options, like bringing as many as 10 retired Perry-class frigates out of retirement for a quick boost in fleet size. But an internal memo[URL]reported;https://www.defensenews.com/naval/2017/11/13/dont-reactivate-the-old-frigate-internal-us-navy-memo-recommends/[/URL]on by Defense News earlier this month found that bringing those ships back would cost over $4 billion, sucking up limited dollars the service needs to modernize the Navy's existing cruisers and destroyers.

The more likely path is using those billions to modernize up to 11 Ticonderoga-class cruisers currently slated for retirement beginning next year, while building dozens of smaller, less expensive ships to fill gaps, according to several analysts.

Without retaining existing vessels, and with little help coming from Congress to build dozens of large, new ships, the other option is to simply stop sailing in some areas, said Jerry Hendrix, a retired U.S. Navy captain who is now at the Center for a New American Security.

"If you start gapping these regions, you create a power vacuum and just like what happened in the South China Sea when we did not pay a lot of attention to it, and the Chinese started to build these artificial islands," he said.

Earlier this month, the Navy released a request for shipbuilders to submit plans for 20 guided missile frigates that would be built quickly, the first of which would be purchased in 2020.

Buying smaller, relatively cheap new frigates and extending the life of current ships offers the best path to a larger fleet, said Bryan Clark, a senior fellow at the Center for Strategic and Budgetary Assessments and former special assistant to the Chief of Naval Operations.

"If Russia or China or North Korea want to start a fight, putting a defenseless ship like an old Perry-class in there certainly won't deter them," Clark said. Having the latest vessels on the front lines with global rivals isn't just a matter of defense, Clark added, it also deters them.

The older ships would also have a difficult time against Russian and Chinese anti-ship cruise missiles and anti-ship ballistic missiles. In order to keep out of the range of those weapons, the Navy is taking a hard look at how it's postured and equipped.

Since the end of the Cold War, the Navy had been able to sail at will, but those days are long gone. "In the South China Sea, we need to sink ships and do it wholesale, and we need to do it at standoff," said David Ochmanek, a senior defense researcher at the Rand Corporation.

That sort of capability requires more ships, and also modernized, long-range weapons that can hit enemies before they ever lay eyes on an American vessel.

The biggest barrier to more ships, however, is cost. The Congressional Budget Office estimated in April that the 355-ship fleet would cost the Navy an average of $102 billion per year to maintain through 2047, as opposed to a $90 billion yearly price tag under the 308-ship plan.

Those numbers would likely be prohibitive, given the current deficit and expected tax cuts.

During the Ronald Reagan George W. Bush defense buildups, "we were starting in a different place fiscally, with an overall debt level for the country that was relatively low," Harrison, the budget analyst, said. "Today, that's not the case."