Senior U.S. Navy leaders have set up a task force to study proposals for a new small warship, as ordered by Defense Secretary Chuck Hagel, and said they would set a new "affordability target" for the ship.

Chief of Naval Operations Admiral Jonathan Greenert and Navy acquisition chief Sean Stackley named the members of the new task force and a separate high-level advisory group in a memorandum dated March 13 that was released on Tuesday.

They told the groups to report back on possible alternatives, including a modified version of the current Littoral Combat Ship (LCS) designs built by Lockheed Martin Corp and Australia's Austal, by July 31 - in time to inform the Pentagon's fiscal 2016 budget deliberations.

"In our efforts to increase the capability and lethality of the small surface combatant force, affordability must remain a critical tenet that informs and guides our decision," the memo said. It said a cost target for the program would be established separately and provided to the task force, but gave no details.

Hagel announced plans on Feb. 24 to stop building the current class of LCS ships after 32 vessels and focus on ships with more firepower and protection, saying he had "considerable reservations" about building all 52 LCS ships as planned.

He said growing threats in the Asia-Pacific region meant the Navy needed to develop small surface ships that could operate in every region and "along the full spectrum of conflict".

The new memo named John Burrow, executive director of Marine Corps Systems Command, to head the task force, as well as eight other officials from across the Navy.

It told the group to develop an initial plan by March 31 for the group's work, including a side-by-side comparison of the capabilities of the FFG 7 class of frigates and the current LCS ships, and a fuller look at threats to the United States and their effect on requirements for a future small surface warship.

The task force will also map out how those military requirements could be met by a modified LCS design, any existing ships and a wholly new ship design, factoring in sensors, weapons, cost, schedule and lethality.

A separate advisory group chaired by Allison Stiller, deputy assistant secretary of the Navy for ships, and Rear Admiral Tom Rowden, director of surface warfare, would include the head of the LCS program, and other senior Navy officials.

Lockheed, Austal and its key supplier, General Dynamics Corp , and Huntington Ingalls Industries, the other major U.S. shipbuilder, are watching closely for details on how the Navy plans to proceed with the new surface warship.

Given declining U.S. military budgets, weapons makers are keen for any new business.

Greenert told reporters last week that a wholly new design would likely be too expensive and take too long to implement.

He said one possibility would be to install some equipment permanently on the current LCS ships, which were designed with modular, interchangeable equipment packages that can be swapped out to hunt for mines, fight submarines or engage in surface warfare, depending on military needs.

Analysts say changes in the current LCS program will likely result in a more expensive ship in the future.