The Pentagon will continue to scale down the size of the armed forces to protect investments in high-tech weapons and cyberwar capabilities, Defense Secretary Chuck Hagel said Tuesday as he laid out how austere times are forcing basic trade-offs in national security priorities.

In a speech that foreshadowed how the U.S. military will be restructured in the coming years, Hagel complained that projected defense budget cuts of $1 trillion during the next decade were “too fast, too much, too abrupt and too irresponsible.”

Like his predecessors, former secretaries Leon E. Panetta and Robert M. Gates, Hagel warned that the cutbacks were eroding military preparedness and morale. But he also sounded a note of resignation, saying that the military would have to come to grips with much smaller budgets and reset expectations as the nation moves “off a perpetual war footing.”

“We do not have the option of ignoring reality or assuming something will change,” Hagel said in an address at the Center for Strategic and International Studies, an influential think tank in Washington.

Hagel’s comments were a recognition that neither his boss, President Obama, nor Congress has shown a willingness to spare the Pentagon from the automatic long-term spending cuts imposed by the Budget Control Act of 2011. With that in mind, Hagel said he has spent much of his time since taking office in February prodding the Defense Department to confront “the stark choices and trade-offs in military capabilities that will be required.”

At the same time, Hagel reminded his audience that even under the worst budget scenarios the Defense Department would have plenty of money. He said that the Pentagon had already “identified opportunities to make changes and reforms” and that even after a retrenchment, the United States alone would still account for nearly 40 percent of all military spending in the world.

“We will need to more efficiently — more efficiently — match our resources to our most important national security requirements,” he said. “We can do things better, and we will.”

Hagel did not reveal any new policies or specific budget proposals but indicated that the military would continue to shrink the size of its conventional land forces in favor of Special Operations troops and weapons that provide “a decisive technological edge.”

“In some cases we will make a shift, for example, by prioritizing a smaller, modern and capable military over a larger force with older equipment,” he said.

In general, Hagel also sought to temper expectations for what the military should do and what it can accomplish. The Pentagon, he said, needs to rely more heavily on allies and should play a supporting role, not a leading role, in U.S. foreign policy.

“We will need to place more of an emphasis on civilian instruments of power, while adapting our military so that it remains strong, capable, second-to-none and relevant in the face of threats markedly different from what shaped it during the Cold War and over the past two decades,” he said.