"We didn't particularly want to do that," he told reporters after his speech Monday at the Navy League's annual symposium in Maryland.
But the White House's decision to trim more than $500 billion from Pentagon coffers over the next decade put the Navy "in a universe of bad decisions," Mabus said.
His comments come days before Navy brass are scheduled to defend that decision, among others included in the service's new shipbuilding plan, before Congress.
The Senate Armed Services Seapower committee and the House Armed Services Oversight and Investigations subpanel plan to dig into the Navy's ship strategy.
The plan calls for a 300-ship fleet over the next five years. Previous Navy estimates had set a 313-ship minimum for the fleet.
Full Armed Services Committee Chairman Buck McKeon (R-Calif.) “will be closely examining” the Navy’s ship-retirement plan, spokesman John Noonan told The Hill in March.
Specifically, McKeon will be looking at whether those retirements are “the right move, given today’s uncertain strategic climate,” he said at the time.
Some defense lawmakers have already begun to second-guess the Navy on the early retirements in recent weeks.
Critics claim the decision is a waste of taxpayer dollars, because pulling those vessels from the fleet early would cut short the return on the investment made by Congress in those ships.
But Mabus reiterated the Navy's argument that it simply costs too much to keep those seven ships in the fleet. The estimated cost to maintain and upgrade those ships totals out to $4.1 billion, according to Mabus.
That said, there is a small window of opportunity to bring those warships back into the Navy fold.
Chief of Naval Operations Adm. Jonathan Greenert is wrapping up a new force requirements assessment. That assessment will detail specifically how many warships the Navy needs and where they should be stationed. It is possible Greenert's study could call for a total fleet size higher than the 300-ship ceiling set under the Navy's newly-minted ship plan.
Mabus declined to comment on whether preliminary findings in Greenert's assessment are pointing toward a larger Navy fleet.