The Pentagon has not yet submitted a shipbuilding blueprint to lawmakers this year because Defense Secretary Mark Esper did not think the Navy has developed a "credible pathway" to building a 355-ship fleet, according to the nominee to head the Pentagon's Cost Assessment and Program Evaluation office.

During his confirmation hearing Tuesday, John Whitley told the Senate Armed Services Committee Tuesday that Esper did not believe the Navy's shipbuilding plan was realistic.

The Navy is required to submit a 30-year plan for shipbuilding to Congress each year with its budget, but has yet to do so this year.

Its failure to provide a 30-year plan has raised concern among lawmakers of both parties.

Whitley said the plan the Navy had produced was not submitted to Congress because it was not, in the eyes of Pentagon officials, "a credible document."

"I think one of the challenges we had with the president's budget submission and why we did not submit the 30-year shipbuilding plan was because it did not have a credible pathway to get there," said Whitley, who is the acting director of CAPE but has by his account pulled back from his responsibilities during the confirmation process. "It assumed resource constraints for five years and then assumed there were no resource constraints. And what the secretary was concerned about was that that was not a credible document to send to you."

According to Whitley, the service needs a fleet larger than the 355-ship benchmark laid out in the 2016 Force Structure Assessment.

"[Esper's] belief is it's a number north of 355. And so what he has tasked the Navy and CAPE to do, and what I would do if confirmed, senator, would be working with the Navy to get a credible path to a number as quickly as possible that's north of 355," Whitley said.

The Navy has advocated for a 355-ship fleet since 2016, and outlined a plan to cap the fleet at 355 last year. It currently consists of roughly 430 ships.