A brawl has broken out at the top rungs of the Pentagon over how to prepare the military for long-term threats, in a rare public fight that pits leaders of the military branches against Defense Secretary Ash Carter.

Carter wants to use the Pentagon's upcoming, approximately $580 billion budget request to solidify the Obama administration's goals of investing in more advanced weapons such as next-generation fighters and submarines, and high-demand skills such as cyber warfare.

But he is butting heads with the Navy's leadership and facing open skepticism from the man in line to be Army secretary, who have disagreed with their boss in recent days over key aspects of the administration's plans. One admiral even mocked critics of a warship program that Carter is trying to scale back.

Carter is getting pushback from multiple quarters.

Navy Secretary Ray Mabus favors more spending on a small, close-to-shore warship that has faced criticism for its lack of firepower and that Carter wants to curtail. At the same time, President Barack Obama's choice for Army secretary, Eric Fanning, expressed qualms last week about the administration's plans to free up money for other priorities by shrinking the number of soldiers.