"The competitive advantage that the United States military has long enjoyed is eroding," Dunford told the Senate Armed Services Committee during a hearing on the Trump administration's defense budget, saying that budget cuts combined with increasingly capable adversaries were both contributing to that erosion.
"In just a few years, if we don't change the trajectory, we will lose our qualitative and our quantitative competitive advantage," Dunford said, warning "the consequences will be profound."
Dunford's warning was specifically focused on the US military's ability to project its power anywhere in the world, something he said was critical to deterring adversaries and reassuring allies that the US can meet its alliance commitments.
Asked to elaborate on the risk by Sen. Deb Fischer of Nebraska, Dunford said that competitors like Russia and China have studied US power projection and have invested in assets that could potentially offset the US military's advantages.
"Since the 1990s, China, Russia, other countries have studied US capabilities from precision munitions to our ability to project power," Dunford said, calling US power projection "our source of strength."
Dunford said Beijing and Moscow were specifically investing in anti-ship cruise missiles, anti-ship ballistic missiles and electronic warfare capabilities, assets he said are designed to prevent US military forces from projecting power around the globe.
A recent Pentagon study found that China's official military budget had grown an average of 8.5% from 2007 to 2016, saying that "Chinese leaders seem committed to increases in defense spending for the foreseeable future, even as China's economic growth slows."
Russia has similarly embarked on a significant military modernization campaign.
"They want to keep us from getting into the area," Dunford told the committee, adding "this is both the case of Russia, with regard to our NATO alliances, and China, with regard to meeting our commitments in the Pacific."
"I don't think there's any question that unless we change the path we're on we're going to be at a competitive disadvantage qualitatively and quantitatively," Dunford said, later adding, "it affects our ability to deter conflict, it affects the confidence that our allies have in our ability to meet our commitments. In the end of the day, it makes a more dangerous world, both nuclear deterrence and conventional deterrence would be affected."
"We would be challenged in projecting power today," Dunford said while pointing out that a Pentagon review of US and adversary capabilities found that the US would "suffer significant casualties and significant time delays in meeting our objectives in projecting power in five years."
Dunford called for a large boost in defense spending in order to ensure that the US military maintained its competitive edge.
"We can maintain our competitive advantage with sustained sufficient and predictable funding," he said. While Dunford called Trump's budget proposal "an essential step," he acknowledged that it alone would be inadequate, calling for continue annual increases in the defense budget of between 3 and 5% above inflation, with 3% the minimum.
He said such increased spending was "necessary to preserve just the competitive advantage we have today and we can't assume that our adversaries will stand still."